Fa"Fad diet" is a term of popular media, not science. Some so-called fad diets may make pseudo-scientific claims. According to one definition, fad diets claim to be scientific but do not follow the scientific method in establishing their validity.

What is a fad diet?
There are many different definitions of what a fad diet consists of. One definition is any weight loss plan that quickly gains popularity and may become unpopular just as quick. A more specific definition is any weight loss program or aid that promises to produce dramatic weight loss in a very short amount of time. Each type of fad diet varies in the amount of food that is restricted and what types of foods may be restricted.
Are fad diets healthy?
The basis of these diets is usually a very restricted diet that may even eliminate certain food groups all together. Research has shown that in order to obtain the amount of nutrients our body needs on a daily basis we must consume a balanced and varied diet. Fad diets do not allow consumers to eat a well-balanced diet in most cases which causes the lack of nutrients to the body. In particular, the diets that eliminate certain foods from a person’s diet completely put the person at risk for nutrient deficiencies. Many of the diet authors will suggest that consumers take daily supplements to make up for the lost nutrients; however supplements do not provide all the plant chemicals and nutrients that our bodies need to function properly. Another risk of these diets is that they produce rapid weight loss but do not teach the person about long-term weight management. There is also a misconception portrayed by the diet authors that there is no need to increase your amount of physical activity for weight loss to occur. Many of these diets actually increase your risks for certain diseases in the long-term, which does not occur with normal weight loss. Finally, these fad diets are often short lived because the person becomes bored of eating the same things all the time, this may cause a person to use multiple diets which can actually alter their metabolism. The constant use of diets will actually slow the person’s metabolism down and make it easier for them to regain the weight once the extreme diet is stopped. Most of the weight lost using a fad diet is water and muscle mass, so the weight is easily regained once the diet is stopped.
Types of Diets and Related Risks:
Diet Type Examples Claims Risks
High Protein - Low
Carbohydrates/
No Carbohydrates
• Dr. Atkins’ New Diet Revolution
• The Carbohydrate Addict’s Diet
• Protein Power
• Sugar Busters
• The Zone
• The South Beach Diet
• Dr. Phil’s Ultimate Weight Solution
• Carbohydrates cause weight gain so they must be limited or eliminated from the diet.
• Ketosis
• Increased Blood Pressure
• Heart Disease
• Nutrient Deficiency
• Dehydration
• Low Caloric Intake
• Kidney Stones
• Bone Loss
• Certain Cancers
• Kidney Disease
Food-Specific
Diets
• Grapefruit
• Cabbage Soup
• Subway
• Peanut butter
• Specific foods cause the body to increase the amount of calories burned • Don’t promote healthy eating habits
• Not nutritionally balanced
• Very low in calories
Liquid Diets • Slim Fast
• Cambridge Diet
• All the nutrients you need in a low calorie form (usually about 400 calories) • Extremely low calorie diets may cause serious illness or even death
• Only works short-term
• Doesn’t teach long-term healthy eating habits
Diet Pills/Aides
• Dexatrim
• Caffeine Pills
• Ephedrine
• Redux
• Phen/Fen
• Hydroxycut
• Dexatrim Natural
• Metabolife 356
• Can help control appetite by taking a pill
• Not scientifically supported
• May contain phenylpropanolamine which can cause: blood pressure elevation, dizziness, nervousness, nausea, insomnia
• Ephedrine may cause: addiction, headaches, high blood pressure, heart palpitations, heart attack
• Not always regulated by the FDA
Pre-measured
Diets
• Jenny Craig
• Nutri-system
• Eating a balanced diet low in fat causes weight loss
• There are good carbs and bad carbs • May not promote healthy eating habits after diet termination
• Costly How to spot a fad diet:
Here are some things to look for that are common in fad diets:
• Blames weight gain on things like blood type, personality, or hormones
• Carries no warnings for individuals with health problems to seek medical advice before beginning the plan • Carries warnings of danger from one of the products
• Discourages drinking water
• Doesn’t address the need for portion control
• Doesn’t allow freedom and flexibility
• Doesn’t recommend or include physical activity
• Encourages unlimited consumption of certain foods
• Forbids or limits certain foods
• Ignores individual differences in weight loss
• Lists good and bad foods
• Must combine certain foods in each meal
• Must pay a good amount of money to get results
• Promises a “quick fix” with little to no effort
• Rapid weight loss, more than 2 pounds a week
• Requires you to purchase a certain product
• Severe limits on carbohydrates or fat
• Simple conclusions drawn from complex studies
• Sounds too good to be true
• Uses testimonials or case studies to show results
• You must drink your daily calorie intake

Top Fad Diets: Love Them or Leave Them?
The gluten-free diet, Fast Diet and Paleo diet are trending. But should they be?
By Toby AmidorJan. 24, 2014One comment SHARE
Each year, a slew of diets – some new and some recycled – are unleashed upon millions of folks looking for the quickest way to shed pounds. Diet promoters promise quick results, and die-hard advocates offer wholehearted testimonials. Many of these diets are targeted to folks who may already have a negative self-image, as well as those looking for the next scientific-sounding diet that really works.

Toby Amidor

Before choosing to embark on any new diet adventure, do your homework to understand what the diet is really about and if it's safe and effective for you. To help you get started, here's an overview of four popular diets:
Gluten-Free Diet
You don't necessarily need to have celiac disease or gluten-sensitivity to embark on this diet. Rather, people are adopting a gluten-free diet to lose weight. All foods containing wheat, barley and rye (such as pasta and traditional baked goods) are avoided, while whole foods like fruits, vegetables, beans, lentils, dairy, healthy fats and seeds are promoted.
Pros:
• Lots of whole foods are included, and these are always healthy choices.
• There is a tendency to steer clear of packaged and processed foods, which tend to be high in sodium and preservatives.
Cons
• A wide variety of gluten-free packaged foods are now available, but many are loaded with more sugar and fat than their gluten-filled counterparts. This makes it easy to splurge, even on gluten-free foods.
• Large portions of any foods (such as gluten-free breads or potato chips) can lead to weight gain.
• Avoiding gluten-containing whole grains can decrease the spectrum of nutrients taken in.
[Read: What is the 'Best Diet' for You?]
Intermittent Fasting
This diet ranked No. 28 of 31 on U.S. News's Best Diets Overall rankings list.
The theory behind it is that our bodies were programmed for periods of feast and famine. As such, we should recreate these feast and famine days in order to lose weight and live a longer life.
On this plan (also called The Fast Diet), dieters select two non-consecutive days each week to eat 500 or 600 calories, depending if they're a man or woman. On fasting days, low-glycemic-index and low-glycemic-load foods are recommended since they take longer to digest, which in turn makes you feel more satisfied. Recommended foods include vegetables, nuts, seeds, legumes (including beans and lentils), and some fruit. Dieters are recommended to follow their regular exercise regimen during fasting days. During the remaining five non-fasting days, you can eat whatever you wish.
Pros
• All food groups are allowed.
• Exercise is promoted.
Cons
• Much of the scientific evidence regarding intermittent fasting is controversial.
• With suboptimal calories consumed twice a week, you may become deficient in several important nutrients.
• Eating so few calories can result in uncomfortable side effects such as headaches, irritability and hunger.
• Lifelong healthy eating habits aren't promoted.
[Read: The Case For Skipping Meals.]
Paleo Diet
This diet ranked dead last on U.S. News's Best Diets Overall rankings list.
The caveman-inspired Paleo diet has a strong following, and revolves around eating like our Paleolithic ancestors – who lived by hunting and gathering. Creators claim that by following this plan, you can increase athletic performance, become naturally lean and eliminate acne. Additionally, the increased consumption of fruits and vegetables is thought to improve symptoms of diseases like osteoporosis, asthma and high blood pressure.
The Paleo diet encourages fresh fruits and vegetables, seafood, lean meat, and healthy fats (such as olive oil and flax seed). It discourages refined sugars and grains, saturated and trans fat, salt-processed foods and yeast, dairy, and whole grains. It also encourages fun and engaging exercise.
Pros
• Lean meats and plenty of fruits and vegetables are recommended.
• This plan tends to be low in sodium.
• Exercise is highly encouraged.
Cons
• Entire food groups – such as whole grains and dairy – are eliminated, making it tougher to take in essential nutrients, including calcium and vitamin D.
• Choosing the wrong types of meat (those that aren't lean) can increase your risk for heart disease.
• Many folks tend to get stuck on the same foods, which limits overall nutrient intake.
• Can be dangerous to follow for those with specific diseases (like kidney disease).
• Purchasing fresh grass-fed and free-range meat, fish and seafood can be pricey.
[Read: Quiz: What Do You Know About the Best Diets?]
Raw Food Diet
This diet ranked No. 29 of 31 on U.S. News's Best Diets Overall rankings list.
The raw food movement has been around for years, but folks are now turning to it in order to lose weight. On this plan, food is never cooked above 116 degrees Fahrenheit in order to keep the food's enzymes intact. Raw foodists emphasize fresh fruits and vegetables, nuts, seeds, herbs, and miso. Off-limits choices include bread, beans, lentils, pasta, meat and eggs. Some followers choose to consume unpasteurized milk and cheese, along with raw fish and meat.
Pros
• Lots of fresh fruits and vegetables are recommended , as are healthy fats from nuts and seeds.
Cons
• Requires tedious meal preparation and special equipment, which can be costly.
• Consuming unpasteurized dairy foods and uncooked fish and meat can lead to foodborne illnesses such as Listeria and E. coli.
• Eliminating numerous food groups (including grains, legumes and animal products) over long periods of time can lead to vitamin deficiencies.
• It's very tough to dine out and have diet-approved food available at social events and parties.
My recommendation: If you're thinking about trying a new weight-loss plan and feel there's something unsafe or questionable, seek the advice of a physician and registered dietitian who can help guide you in the right direction. Your health and well-being should be your number one concern. To find a registered dietitian in your area, log onto Academy of Nutrition and Dietetics website and click on the green button that says "Find A Registered Dietitian."
[Read: 2014 Food Trends: What's Hot at Restaurants.]
Hungry for more? Write to eatandrun@usnews.com with your questions, concerns and feedback.
Toby Amidor , MS, RD, CDN, is the owner of Toby Amidor Nutrition and author of the forthcoming cookbook "The Greek Yogurt Kitchen" (Grand Central Publishing 2014). She consults and blogs for various organizations including FoodNetwork.com's Healthy Eats Blog and Sears' FitStudio.

If you've followed a fad diet, you have plenty of company. But have you been able to stay on these deprivation diets for a long time? And if you did lose weight, did the pounds stay off once you went back to your usual way of eating?
The truth is fad diets don't work to help you keep the weight you lose off long-term.
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Read the Biggest Loser Winning Workout and Meal Plan article > >
So what does work? Here's some simple, straightforward advice.
Variety Is Key
Just as a car needs the proper gasoline to make it run, a body needs a healthy diet to develop properly. That means the right balance of protein, carbohydrates, and fat -- as well as a host of other nutrients.
When you go on a fad diet and exclude necessary nutrients, you're putting yourself at risk for becoming ill. Getting too little of any nutrient may not cause an immediate problem. But if it's lacking for a long time, you may find you have health problems.
Practice Portion Control
America's obesity epidemic may not come solely from the type of foods people eat but also from the portion sizes. Food servings have grown larger and larger over the years. And fast food restaurants aren't the only places you'll find super-sized meals. Researchers have noted that from 1970 through the 1990s, portion sizes of foods such as hamburgers, burritos, tacos, French fries, sodas, ice cream, pie, cookies, and salty snacks increased -- whether the foods were eaten at home or at restaurants.
Just what does a healthy serving size look like? Here are some guidelines to keep in mind: * A cup of fruit should be no larger than your fist. * One ounce of meat or cheese is about the same as the size of your thumb from base to tip. * Three ounces of meat, fish, or poultry (a normal serving) is about the size of your palm. * One to two ounces of nuts equals your cupped hand.
Here are some more tips to help with portion (and calorie) control: * Serve your meals on salad plates instead of large dinner plates. * Store snack foods in tiny sandwich bags so you are sure you're eating no more than one portion. * When ordering out, share your entrée with a friend. * Ask for a kids' meal or small size. Never go for a super-size portion. * Fill up on fresh green salads, fruit, and vegetables instead of high-fat foods, breads, pasta, and desserts. Simple Strategies for Losing Weight
The best diet is not a diet at all but a way of life that includes food you enjoy, exercise, and healthy habits. * Eat a variety of foods -- lean protein; complex carbohydrates such as whole grains, fruits, and vegetables; and "good" fats, like omega-3 fats from fish and monounsaturated fats from avocados, nuts, and olives or olive oil. * Say NO to bad fats: minimize how much saturated fat you get from animal sources, and eliminate trans fats from the fried foods, snacks, and fast food products you eat. * Eat at least five servings of fruits and vegetables each day. Choose different colors of fruits and vegetables to ensure optimal nutrition. * Be careful about portion sizes. If you must have seconds, serve yourself vegetables. * Exercise at least 150 minutes each week with a moderately intense activity like brisk walking. This can be divided into smaller blocks of time. For example, you could do a brisk walk for 10 minutes three times a day for five days to reach 150 minutes. * Clean out the kitchen and eliminate all junk food. Toss out high-calorie, high-fat, sugary foods that will tempt you to overeat -- chips, cookies, crackers, ice cream, candy bars, and the like. * Fill your kitchen with lean protein, fruits and vegetables, whole grains, legumes, nuts and seeds, good fats, and fat-free or low-fat dairy products. * Eat smaller meals more frequently. Five to six per day may be best. Space your meals every three to four hours throughout your day. Try taking low fat cheese and whole grain crackers to school or work for a snack, or eat a tablespoon of peanut butter with one slice of whole grain bread. Find foods that are healthy and that keep you full. * If you like lots of food on your plate, fill up with a large salad and a super serving of green beans, broccoli, cabbage, kale, or other low calorie vegetable. * Snack on berries. Dark berries (blueberries, blackberries, cherries, and raspberries) are rich in healthy antioxidants. They are also low in calories and fat and high in fiber. * Avoid "empty calories" including sugar-containing sodas and fruit drinks.
Losing Weight Without Fad Diets
(continued)
Simple Strategies for Losing Weight continued...
If you need more information on weight loss and dieting, talk to your health care provider or a registered dietitian. Ask your doctor about your "ideal" weight and the number of calories you need to lose pounds and maintain an ideal weight.
Also, ask friends, family, or coworkers to join you as you work to change your eating habits and pare down your weight. Sticking to a weight loss plan is much easier when you have someone to support you.
Many dieters are still trying to find the magic bullet toweight loss. WebMD gets the skinny from experts onthe latest quick-fix diets.
-------------------------------------------------
WebMD Feature Archive
By Carolyn J. Strange
WebMD Feature
Reviewed by Louise Chang, MD
When singer Beyoncé Knowles needed to lose 22 pounds in a hurry for her role inthe film Dreamgirls, she went on a crash diet that consisted of drinking a mixture ofwater, cayenne pepper, and maple syrup as a substitute for regular meals. She lostthe weight, and in the process sparked a run on maple syrup as news and photos ofher newly svelte figure spread. But even Beyoncé has been quick to tellinterviewers, "I would not recommend it if someone wasn't doing a movie, becausethere are other ways to lose weight."
Beyoncé's own caution to dieters probably comes as good news to nutritionists whodon't think much of her quick-fix weight loss plan. "This diet is void of essentialnutrients and probably doesn't promote healthful eating and lifestyle habits thatwould sustain any weight that is lost," says Jenna Anding, PhD, RD, LD, associatedepartment head, department of nutrition and food science, Texas A&M University."Also, losing 20 pounds in two weeks is not healthy; nutrition experts recommend aweekly weight loss of no more than 2 pounds per week."
Our Fascination With Fad Diets
The "syrup diet" is just one of the many diet plans (albeit one of the more extreme)to capture our weight-crazed fancy over the years. From Atkins to South Beach tothe Zone to the Blood Type Diet -- to name just a few -- many of us are always onthe lookout for the "magic bullet" that will help us shed pounds quickly, and more orless effortlessly.
Why, despite the advice of most nutrition experts, are we fascinated by the myriaddiet plans crowding bookstore shelves? "Most individuals want cutting-edgesolutions for weight loss, and fad diets offer, at least on the surface, 'new' ways tobeat the boring mathematical reality of long-term weight loss," explains RobinSteagall, RD, nutrition communications manager for the Calorie Control Council.
"All diets work on the principle of cutting calories [cutting 500 calories a day canresult in a 1-pound weight loss in a week]," Steagall adds, "but every new diet hassome unique twist to accomplish this mission."
Among the newest, for example, is The Fast-Food Diet, co-authored by StephenSinatra, MD, and Jim Punkre, which capitalizes on the American love affair with,yes, fast food. While the diet doesn't promote fast food per se, it acknowledges thatmany of us (on any given day, the authors say, 25% of our population) visit fast-foodrestaurants because they're convenient and affordable.
So, they suggest, if you're there already, make healthy choices that can lead toweight loss. Some tips: Choose the smallest drink size, or better yet, switch fromsoda to club soda or water; order from the children's menu; or eat a baked potato,not fries.
Weight Control Secret: Energy Balance
Learn how to balance calories in with calories out
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By Kathleen M. Zelman, MPH, RD, LD
WebMD Weight Loss Clinic - Expert Column
What do you think of when you hear the term 'energy balance' -- maybe a skateboard stunt or a yoga pose? What it really means, at least in the health care community, is the art of consuming just the right number of calories to manage yourweight.
You're probably familiar with the balancing act of juggling career, family, friends, community, and personal needs. In weight control, the "balancing act" means taking in only as much food and drink as you need to fuel your body's basic functions, the activities of daily living, and exercise.
The number of calories needed for energy balance is highly individual, and it changes from day to day depending on your activity level. Weighing in once weekly (or even more often) is the easiest method to determine whether you're in energy balance. If you take in more calories than you burn, they will likely show up as weight gained, while creating a calorie deficit sends the needle on the scale counterclockwise.
Beyond Counting Calories
Counting calories can be labor-intensive, and can take all the fun out of eating. So instead of fixating on calories, think food, glorious food! Choosing foods that are high in fiber, fluid, and nutrients that fill you up on fewer calories is the secret to painless calorie cutting.
Fruits, vegetables, beans, whole grains, low-fat dairy, and small portions of lean meats and nuts are the kind of foods you should be enjoying each day. Unprocessed foods (those in their natural form) are the healthiest options at the grocery store.
If you enjoy eating refined, processed foods, do so in moderation to better control your calorie intake.
Calories and Exercise
A healthy dose of regular physical activity will boost your metabolism in two ways. Every time you move, you burn calories. Exercise also builds muscle, and the more muscle you have, the more calories you need simply to maintain your basal metabolism (the number of calories required for digestion, breathing, blood circulation, and other body processes while you're at rest).
Of course, energy balance is not the only benefit of regular exercise. That list includes weight loss, stronger muscles and bones, lower blood pressure and cholesterol levels, and a healthier heart - not to mention disease prevention and a longer life.
Exercise is a critical part of weight control and good health, but the truth is that, at least for some people, it can also send your appetite into overdrive. Don't fall into the trap of thinking that exercising gives you license to scarf down cheeseburgers and donuts. The trick is to ease your hunger with satisfying foods that taste good and are low in calories.
It's also a good idea to fuel up before your workout. Go for healthy, balanced snacks that include lean protein, complex carbs, fiber, and/or small amounts of fat (try whole-grain cereal with berries and low-fat milk; half a whole-grain bagel with peanut butter and banana slices; a smoothie made with low-fat yogurt, fresh fruit, and orange juice; or brown rice and steamed veggies sprinkled with a little cheese).
Weight Control Secret: Energy Balance
Learn how to balance calories in with calories out
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Calories and Exercise continued...
It's also important to stay well hydrated so you won't mistake thirst for hunger. It's easy to overindulge in sports drinks and fruit juices that satisfy thirst but can add lots of extra calories. Try good old-fashioned water to quench your thirst before and after your workouts.
If you don't exercise each day, eat a little more on the days you work out and less on days you are less active. Some people complain they eat more on those less active days simply because of boredom. Instead of reaching for something extra to eat, lace up your sneakers and take a walk!
7 Tips for Achieving Energy Balance
Here are some more tips for striking the right energy balance: * Reshape your plate. Increase the proportion of vegetables, salads, fruits, beans, and whole grains to cover two-thirds of your plate. * Fill the other third of the plate with lean meats and poultry, fish (especially fatty fish like tuna or salmon), or low-fat dairy. * Make sure your portions are under control. Once in a while, get out the food scale and measuring cups to remind yourself of what a normal portion should look like. * Schedule your exercise first thing in the morning so it won't get crowded out of your day. * Alternate your exercise activities (maybe try a new class) so you won't get bored and your muscles will get a better workout. * Power past any weight loss plateaus by increasing the intensity of your workouts. Try turning up the incline on the treadmill, or adding speed intervals to your exercise bike routine. * Keep track of what you eat in a food journal to avoid unconscious overeating. * The ABCs of Weight Loss * We've got 26 tips to help you succeed. * Save This Article For Later * Share this: * Font size: * AAA * By Kathleen M. Zelman, MPH, RD, LD
WebMD Weight Loss Clinic - Expert Column * Think you know your ABCs? I'm not talking about the classroom basics you learned in first grade, but the fundamentals of weight loss success. Here are 26 of my best diet tips, from A to Z: * A is for attitude. A can-do attitude will help you get over the inevitable hurdles of weight loss. Anticipate slip-ups -- they happen. But instead of letting them derail your weight loss efforts, learn from them and get right back on track. You don't have to be perfect to lose weight and be healthy. Just keep your eye on the target and keep moving forward, one step at a time. * B is for breakfast. It really is the most important meal of the day. Don't leave home without eating something nutritious to get your metabolism perking and give you energy for the day ahead. It can be a banana, low-fat yogurt, cereal, last night's leftovers, etc. A small meal that contains both fiber and protein can keep you feeling satisfied until lunchtime. * C is for calories. They do count. Get into the habit of reading food labels to help you make healthy choices. And keep in mind that all the information listed there is based on the portion size the label specifies (which may not be the size of the portion you usually eat). Monitoring your portions and learning more about the calories in the foods you enjoy will help you meet your goals. * Diets don't work. There are hundreds of diets that will help you lose weight, but what good is losing weight if you gain it right back? Eating crazy food combinations or eliminating food groups is not the way to keep weight off. Instead, choose a nutritionally balanced plan with enough calories to keep you from feeling famished (like the WebMD Weight Loss Clinic eating plans). * Eating regular meals is essential. Experts agree that you should go no longer than 4 to 5 hours between meals. Otherwise, intense hunger can trigger a binge. Some experts believe dieters have better control if they eat several mini-meals throughout the day. Choose the meal pattern that works best in your lifestyle, but make sure to eat at least three meals per day. * Fiber is nature's weight loss aid. It comes in two forms, soluble (the gummy type found in oatmeal and beans) and insoluble (the type found in fruits, vegetables, and whole grains). Both are important to good health. Soluble fiber can help to lower cholesterol; insoluble contains indigestible fibers that add bulk to our diets. Both forms of fiber swell in the stomach and help to create a feeling of fullness. Most high-fiber foods are also high in water and low in calories, making them must-have diet foods.

Lots of today's popular diets take advantage of our desire to drop weight quickly. Unfortunately, though, "quick-fix" diets don't work.
Here are 5 clues that a diet may be more about empty promises than real results: 1. The diet is based on drastically cutting back calories.Starvation-type diets that require the body to fast often promise quick results. But our bodies simply aren't designed to drop pounds quickly. In fact, doctors say it's nearly impossible for a healthy, normally active person to lose more than 2 to 3 pounds per week of actual fat, even on a starvation diet.

Here's the trick that very low-calorie diets rely on: The body's natural reaction to near-starvation is to dump water. So most, if not all, of the weight lost on quick-weight-loss diets is not fat — it's just water. And the body sucks this lost water back up like a sponge once a person starts eating normally again. 2. The diet is based on taking special pills, powders, or herbs.These are usually just gimmicks — and the only thing they slim down is your wallet.

Some diet pills contain laxatives or diuretics that force a person's body to eliminate more water. Just like restricted-calorie diets, the weight lost with these supplements is mostly water, not fat.

Other supplements claim that their ingredients speed up metabolism; suppress appetite; or block the absorption of fat, sugars, or carbohydrates. For most diet supplements, there's no reliable scientific research to back up their claims. And doctors consider diet supplements risky for teens because not much is known about how the ingredients affect the growing body. 3. The diet tells you to eat only specific foods or foods in certain combinations. There's no reliable scientific proof that combining certain foods works. And limiting the foods you eat means you might not get all the nutrition you need. 4. The diet makes you completely cut out fat, sugar, or carbs.Depriving our bodies of needed food groups is a bad idea (especially when they're still growing). It's better to eat smaller portions in well-rounded meals (meals that contain lean protein, whole grains, fruits, veggies, and low-fat dairy). When your body gets the right balance of nutrition, it's less likely to send you willpower-busting cravings! Eating smaller portions also helps you set good eating habits that will help you keep the weight off. 5. The diet requires you to skip meals or replace meals withspecial drinks or food bars. As with diets that ban certain food groups, skipping or substituting meals can mean you don't get the nutrition needed to support healthy development. Plus, you miss out on the enjoyment of sharing a satisfying meal with friends or family.
Reviewed by: Mary L. Gavin, MD
Date reviewed: October 2013 * For Teens

How Can I Spot a Fad Diet?
With so many popular diets to choose from, how can you select the right one? It may be a fad diet if it: * Sounds too good to be true, it probably is. “Lose 15 lbs in 7 days!” * Recommends using a single food on a very consistent basis. * Promises quick and easy weight loss with no effort. * Eliminates an entire food group such as carbohydrates or dairy. * Guarantees an outcome in a specified time period. * Bases evidence for effectiveness only on the quotes of other dieters.

Spot a Faulty Fad Diet
No carbs? No fat? Any fad diet or extreme weight loss plan that requires cutting complete food groups out of your nutrition plan will not provide you with the proper nutrition you need. Despite the fact that they claim cutting carbohydrates and fats will lead to weight loss, your body needs these nutrients to stay healthy. In fact, eating whole grains high in dietary fiber and healthy oils has been shown to help manage a healthy weight.
Carbohydrates
These are your body's main source of fuel. Eating whole grains that are high in dietary fiber is important in intestinal health and waste elimination. Try healthy carbohydrates like sweet potatoes, celery, peaches, beans, yogurt and whole-grain pastas, breads, cereals, and crackers.
Fats
These are essential for normal growth and development, absorbing certain vitamins and providing your body with energy. Add olive or canola oil to your salads, snack on a handful of nuts, spread nut butters on whole-wheat toast, and try cooking fatty fish two times a week.
For more information on leading a healthier lifestyle, consult a registered dietitian in your area.

Should We Eat Like Our Caveman Ancestors?

Reviewed by Sharon Denny, MS, RDN
The Paleolithic (Paleo) diet, also called the "Caveman" or "Stone Age" diet, centers around the idea that if we eat like our ancestors did 10,000 years ago, we'll be healthier, lose weight and curb disease. "A quick and pithy definition of the Paleo diet is—if the cavemen didn't eat it then you shouldn't either," says Academy Spokesperson Jim White, RDN, ACSM/HFS. That means foods that can be hunted, fished or gathered: meat, fish, shellfish, poultry, eggs, veggies, roots, fruits and berries. No grains, no dairy, no legumes (beans or peas), no sugar, no salt. Why? "According to proponents, our bodies are genetically predisposed to eat this way. They blame the agricultural revolution and the addition of grains, legumes and dairy to the human diet for the onset of chronic disease (obesity, heart disease, and diabetes)," says White.
On one hand, this way of eating encourages including more fruits and vegetables and cutting out added sugar and sodium—which aligns with the 2010 Dietary Guidelines for Americans. The combination of plant foods and a diet rich in protein can help control blood sugar, regulate blood pressure, contribute to weight loss and prevent Type 2 diabetes, says White.
But a typical plan also exceeds the Dietary Guidelines for daily fat and protein intake and falls short on carbohydrate recommendations, according to a review from U.S. News & World Report. The exclusion of whole grains, legumes and dairy can be risky as well. "These foods are nutrient-rich and contain important vitamins and minerals such as calcium and vitamin D. Without these foods, supplementation is necessary," says White. "Eating this way … can be very healthy but the lack of certain foods may result in certain deficiencies."
Eliminating whole grains and dairy is not necessarily the ticket to ending disease and ensuring weight loss. Whole grains contain dietary fiber, which may help reduce your risk of heart disease, cancer and diabetes, and other health complications. And studies suggest that dairy may play a role in weight loss. "The crux of the problem, with respect to grains and dairy, stem from over consumption, and as with anything, excess quantities will become problematic," explains White.
The Paleo diet might also be hard to sustain. "We live in a society where it is not possible to eat exactly as our ancestors ate. For example, wild game is not readily available as most of the meat we consume has been domesticated. And the plant food we eat has also been processed rather than grown and gathered in the wild," says White. "While strict conformity is not realistic, it is possible to modify the plan, eating only wild caught fish, grass-fed meat, and organic fruits and vegetables." But even that can be hard to follow because of lack of variety, need for planning, supplementation and cost, White adds.
More Information:

Overview
Type:

Low-carb.
Resembles these U.S. News-rated diets: Atkins, Eco-Atkins
The aim: May include weight loss and maintenance, and prevention or control of many “diseases of civilization,” like type 2 diabetes and heart disease.
The claim: You’ll lead a healthier, fitter, disease-free life.
The theory: Our highly processed, carb-obsessed eating pattern is the culprit behind many of our biggest health ills, so why not go back—way back—to the Paleolithic period of more than 10,000 years ago, when our diet wasn’t full of junk food and pasta? Paleo advocates say we should eat the way we ate when we were hunting and gathering: animal protein and plants.
How does the Paleo Diet work?
Paleo diets are based on a simple premise—if the cavemen didn’t eat it, you shouldn’t either. So long to refined sugar, dairy, legumes, and grains (this is pre-agricultural revolution); hello to meat, fish, poultry, fruits, and veggies. What you eat and how much depend on your goals or the specific program you’re on, if you choose to follow one.
Read More
Will you lose weight?
No way to tell. Paleo diets haven’t yet drawn the attention of many researchers. One tiny study that looked at weight loss found that 14 participants lost an average of about 5 pounds after three weeks on a Paleo regimen. (But even the researchers called their study “underpowered.”) Still, if you build a “calorie deficit” into your Paleo plan—eating fewer calories than your daily recommended max, or burning off extra by exercising—you should shed some pounds. How quickly and whether you keep them off is up to you.
Does it have cardiovascular benefits?
Unknown. While some studies have linked Paleo diets with reducing blood pressure, bad “LDL” cholesterol, and triglycerides (a fatty substance that can raise heart disease risk), they have been few, small, and short. And all that fat would worry most experts.
Can it prevent or control diabetes?
Unknown.
Read More
Are there health risks?
Possibly. By shunning dairy and grains, you’re at risk of missing out on a lot of nutrients. Also, if you’re not careful about making lean meat choices, you’ll quickly ratchet up your risk for heart problems.
While there are no specific dieter restrictions, you’ll want to consider talking with your doctor before making changes to your meal plans.

The paleolithic diet is a modern nutritional plan based on the presumed diet of Paleolithic humans. It is based on the premise that human genetics have scarcely changed since the dawn of agriculture, which marked the end of the Paleolithic era, around 15,000 years ago, and that modern humans are adapted to the diet of the Paleolithic period.
The Paleolithic diet consists mainly of fish, grass-fed pasture raised meats, eggs, vegetables, fruit, fungi, roots, and nuts, and excludes grains, legumes, dairy products, potatoes, refined salt, refined sugar, and processed oils. Certain portions should be established for balance of nutrients to maintain homeostasis.[1][2]
Proponents argue that modern human populations subsisting on traditional diets, allegedly similar to those of Paleolithic hunter-gatherers, are largely free of diseases of affluence[3][4] and that Paleolithic diets in humans have shown improved health outcomes relative to other widely-recommended diets.[5][6]
The paleolithic diet is a controversial topic among dietitians[7][8] and anthropologists.[9][10] An article on the website of the National Health Service of the United Kingdom Choices refers to it as a fad diet.[11]
The Paleolithic diet is also known as the "paleo diet", "paleodiet", "caveman diet", "Stone Age diet", and "hunter-gatherer diet".[citation needed]
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History[edit]
First popularized in the mid-1970s by gastroenterologist Walter L. Voegtlin,[12][13] it has been promoted and adapted by a number of authors and researchers in several books and academic journals.[9] A common theme in evolutionary medicine,[14][15] Gastroenterologist Walter L. Voegtlin was one of the first to suggest that following a diet similar to that of the Paleolithic era would improve a person's health.[13] In 1975, he self-published The Stone Age Diet: Based on In-depth Studies of Human Ecology and the Diet of Man,[12] in which he argued that humans are carnivorous animals. He noted that the ancestral Paleolithic diet was that of a carnivore — chiefly fats and protein, with small amounts of carbohydrates.[16][17] His dietary prescriptions were based on his own medical treatments of various digestive problems, namely colitis, Crohn's disease, irritable bowel syndrome and indigestion.[18][19]
In 1985, S. Boyd Eaton and Melvin Konner published a paper on Paleolithic nutrition in the New England Journal of Medicine,[20] which attracted wider mainstream medical attention to the concept.[21] Three years later, Eaton, Konner, and Marjorie Shostak published a book about this nutritional approach,[22] which was based on achieving the same proportions of nutrients (fat, protein, carbohydrates, vitamins, and minerals) as were present in the diets of late Paleolithic people. It did not exclude foods that were not available before the development of agriculture. As such, this nutritional approach included skimmed milk, whole-grain bread, brown rice, and potatoes prepared without fat, on the premise that such foods supported a diet with the same macronutrient composition as the Paleolithic diet.[16][23][24] In 1989, these authors published a second book on Paleolithic nutrition.[25][26]
Starting in 1989, Staffan Lindeberg led scientific surveys of the non-westernized population on Kitava, one of the Trobriand Islands of Papua New Guinea. These surveys, collectively referred to as the Kitava Study, found that this population apparently did not suffer from diabetes, hypertension,ischemic heart disease, obesity, or strokes. Starting with the first publication in 1993,[27] scholars with the Kitava Study have published a number of scientific works on the relationship between diet and western disease.[28] In 2003, Lindeberg published a Swedish-language medical textbook on the subject.[29] In 2010, this book was wholly revised, updated, translated and published for the first time in English.[30]
Since the end of the 1990s, a number of medical doctors and nutritionists[31][32][33] have advocated a return to a so-called Paleolithic (preagricultural) diet.[9] Proponents of this nutritional approach have published books[34][35][36] and created websites[37][38][39][40] to promote their dietary prescriptions.[41][42][43][44][45] They have synthesized diets from modern foods that emulate nutritional characteristics of the ancient Paleolithic diet. Some of these allow specific foods that would have been unavailable to pre-agricultural peoples, such as some animal products (i.e., dairy), processed oils, and beverages.[34][46][47]
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Practices[edit]

Raw Paleolithic-style dish: sashimi (raw fish) dinner set
The Paleolithic diet seeks to mimic the diet of preagricultural foragers; it generally corresponds to what was available in any of the ecological niches of Paleolithic humans.[1][2] Based upon commonly available modern foods, it includes cultivatedplants and domesticated animal meat as an alternative to the wild sources of the original pre-agricultural diet.[1][48] The ancestral human diet is inferred from historical and ethnographic studies of modern-day forages as well as archaeological finds,anthropological evidence and application of optimal foraging theory.[49][50][51][52]
The Paleolithic diet consists of foods that can be fished and hunted, such as seafood and meat (including offal), and foods that can be gathered, such as eggs, fruits, herbs, insects, mushrooms, nuts, seeds, spices, and vegetables.[1] The meats recommended for consumption are preferably free of food additives, such as wild game meats and grass-fed beef, since they contain higher levels of omega-3 fats compared with grain-produced domestic meats.[1][48][53] Food groups that advocates claim were rarely or never consumed by humans before the Neolithic agricultural revolution are excluded from the diet, mainly dairy products, grains, legumes (e.g., beans and peanuts), processed oils, refined sugar, and salt.[1] Many of these foods would have been available at certain times of the year, and may or may not have been consumed. Some advocates consider the use of oils with low omega-6/omega-3 ratios, such as olive oil, to be healthy and advisable.[48]

Paleolithic-style dish: roast pork with cooked and raw vegetables and fruit
On the Paleolithic diet, practitioners are permitted to drink mainly water, and some advocates recommend tea as a healthy drink.[48] Eating a wide variety of plant foods is recommended to avoid high intakes of potentially harmful bioactive substances, such as goitrogens, which are present in some roots, seeds, and vegetables.[1][50][54] Unlike raw food diets, all foods may be cooked, without restrictions.[1][55] But, there are Paleolithic dieters who believe that humans have not adapted to cooked foods, and so they eat only foods which are both raw and Paleolithic.[56][57]
According to certain proponents of the Paleolithic diet, practitioners should derive about 56–65% of their food energy from animal foods and 36–45% from plant foods. They recommend a diet high in protein(19–35% energy) and relatively low in carbohydrates (22–40% energy), with a fat intake (28–58% energy) similar to or higher than that found in Western diets.[48][58][59]
Staffan Lindeberg advocates a Paleolithic diet, but does not recommend any particular proportions of plants versus meat or macronutrient ratios.[1][50] According to Lindeberg, calcium supplementation may be considered when the intake of green leafy vegetables and other dietary sources of calcium is limited.[1]
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Rationale and evolutionary assumptions[edit]
According to S. Boyd Eaton, "we are the heirs of inherited characteristics accrued over millions of years; the vast majority of our biochemistry and physiology are tuned to life conditions that existed before the advent of agriculture some 10,000 years ago. Genetically our bodies are virtually the same as they were at the end of the Paleolithic era some 20,000 years ago."[60]
Therefore, an ideal diet for human health and well-being is one that resembles this ancestral diet.[2][49]
The reasoning underlying this nutritional approach is that natural selection had sufficient time to genetically adapt the metabolism and physiology of Paleolithic humans to the varying dietary conditions of that era. But in the 10,000 years since the invention of agriculture and its consequent major change in the human diet, natural selection has had too little time to make the optimal genetic adaptations to the new diet.[1][2] Physiological and metabolic maladaptations such as diabetes have been seen in Native Americans populations newly introduced to the contemporary Western diet.[61]
More than 70% of the total daily energy consumed by all people in the United States comes from foods such as alcohol, cereals, dairy products, refined sugars, and refined vegetable oils. Advocates of the Paleolithic diet assert these foods contributed little or none of the energy in the typical preagricultural hominin diet[49] and argue that excessive consumption of these novel Neolithic and industrial-era foods is responsible for the current epidemic levels of cancer, cardiovascular disease, high blood pressure, obesity, osteoporosis, and type 2 diabetes in the US and other contemporary Western populations.[49]
Supporters also point to several potentially therapeutic nutritional characteristics of preagricultural diets.[49][62][63][64]
Physical activity[edit]
Researchers have applied the evolutionary rationale to the paleolithic lifestyle to argue for high levels of physical activity in addition to dietary practices. They suggest that human genes "evolved with the expectation of requiring a certain threshold of physical activity", and the sedentary lifestyle results in abnormal gene expression.[65][66] Compared to ancestral humans, modern humans often have increased body fat and substantially less lean muscle, which is a risk factor for insulin resistance.[67] Human metabolic processes were evolved in the presence of physical activity–rest cycles, which regularly depleted skeletal muscles of their glycogen stores.[68] To date, it is unclear whether these activity cycles universally included prolonged endurance activity (e.g., persistence hunting) and/or shorter, higher intensity activity. S. Boyd Eaton estimated that ancestral humans spent one-third of their caloric intake on physical activity (1000 cal/day out of the total caloric intake of 3000 cal/day),[69] and that the paleolithic lifestyle was well approximated by the WHO recommendation of the physical activity level of 1.75, or 60 minutes/day of moderate-intensity exercise.[70] L. Cordain estimated that the optimal level of physical activity is on the order of 90 cal/kg/week (900 cal/day for a 70 kg human.)[66]
Opposing views[edit]
Critics have questioned the accuracy of the science on which the diet is based. John A. McDougall (M.D), author of The Starch Solution, attempted to discredit the science used to determine the Paleolithic diet, and proposed that the human diet around this time was instead based primarily on starches.[citation needed]
The evolutionary assumptions underlying the Paleolithic diet have been disputed.[10][23][71][72] According to Alexander Ströhle, Maike Wolters and Andreas Hahn, with the Department of Food Science at the University of Hanover, the statement that the human genome evolved during thePleistocene (a period from 1,808,000 to 11,550 years ago) rests on the gene-centered view of evolution, which they believe to be controversial.[72] They rely on Gray (2001)[73] to argue that evolution of organisms cannot be reduced to the genetic level with reference to mutation, and that there is no one-to-one relationship between genotype and phenotype.[72] They further question the notion that 10,000 years is an insufficient period of time to ensure an adequate adaptation to agrarian diets.[72] They note that alleles conferring lactose tolerance increased to high frequencies in Europe just a few thousand years after animal husbandry was invented. Recent increases in the number of copies of the gene for salivary amylase, which digests starch, appear to be related to the development of agriculture.[74] Referring to Wilson (1994),[75] Ströhle et al. argue that "the number of generations that a species existed in the old environment was irrelevant, and that the response to the change of the environment of a species would depend on the heritability of the traits, the intensity of selection and the number of generations that selection acts."[76] They state that if the diet of Neolithic agriculturalists had been in discordance with their physiology, then this would have created a selection pressure for evolutionary change. Modern humans, such as Europeans, whose ancestors have subsisted on agrarian diets for 400–500 generations, should be somehow adequately adapted to it. In response to this argument, Wolfgang Kopp states that "we have to take into account that death from atherosclerosis and cardiovascular disease (CVD) occurs later during life, as a rule after the reproduction phase. Even a high mortality from CVD after the reproduction phase will create little selection pressure. Thus, it seems that a diet can be functional (it keeps us going) and dysfunctional (it causes health problems) at the same time."[76] Moreover, S. Boyd Eaton and colleagues have indicated that "comparative genetic data provide compelling evidence against the contention that long exposure to agricultural and industrial circumstances has distanced us, genetically, from our Stone Age (sic) ancestors";[4] however, they mention exceptions such as increased lactose and gluten tolerance, which improve ability to digest dairy and grains, while other studies indicate that human adaptive evolution has accelerated since the Paleolithic.[77]
Referencing Mahner et al. (2001)[78] and Ströhle et al. (2006),[79] Ströhle et al. state that "whatever is the fact, to think that a dietary factor is valuable (functional) to the organism only when there was ‘genetical adaptation’ and hence a new dietary factor is dysfunctional per se because there was no evolutionary adaptation to it, such a panselectionist misreading of biological evolution seems to be inspired by a naive adaptationistic view of life."[72]
Katharine Milton, a professor of physical anthropology at the University of California, Berkeley, has also disputed the evolutionary logic upon which the Paleolithic diet is based. She questions the premise that the metabolism of modern humans must be genetically adapted to the dietary conditions of the Paleolithic.[10] Relying on several of her previous publications,[80][81][82][83] Milton states that "there is little evidence to suggest that human nutritional requirements or human digestive physiology were significantly affected by such diets at any point in human evolution."[10]
There is some evidence suggesting that Paleolithic societies were processing cereals for food use at least as early as 23,000 BCE. These findings are a matter of dispute.[84][85][86][87][88]
Plant-to-animal ratio[edit]
The specific plant to animal food ratio in the Paleolithic diet is also a matter of some dispute. The average diet among modern foraging societies is estimated to consist of 64–68% of animal calories and 32–36% of plant calories,[59][89] with animal calories further divided between fished and hunted animals in varying proportions (most typically, with hunted animal food comprising 26–35% of the overall diet). As part of the Man the Hunter paradigm, this ratio was used as the basis of the earliest forms of the Paleolithic diet by Voegtlin, Eaton and others. To this day, many advocates of the Paleolithic diet consider high percentage of animal flesh to be one of the key features of the diet.
However, great disparities do exist, even between different modern foraging societies. The animal-derived calorie percentage ranges from 25% in the Gwi people of southern Africa, to 99% in Alaskan Nunamiut.[90] The animal-derived percentage value is skewed upwards by hunting-oriented polar foraging societies, who have no choice but to eat animal food because of the inaccessibility of plant foods. Since those environments were only populated relatively recently (for example, Paleo-Indian ancestors of Nunamiut are thought to have arrived in Alaska no earlier than 30,000 years ago), such diets represent recent adaptations rather than conditions that shaped human evolution during much of the Paleolithic. More generally, hunting and fishing tend to provide a higher percentage of energy in forager societies living at higher latitudes. Excluding cold-climate and equestrian foragers results in a diet structure of 52% plant calories, 26% hunting calories, and 22% fishing calories.[89] Furthermore, those numbers may still not be representative of a typical Paleolithic diet, since fishing did not become common in many parts of the world until the Upper Paleolithic period 35-40 thousand years ago,[91] and early humans' hunting abilities were relatively limited,[dubious – discuss] compared to modern foragers, as well (the oldest incontrovertible evidence for the existence of bows only dates to about 8000 BCE,[92] and nets and traps were invented 20,000 to 29,000 years ago).
Another view is that, up until the Upper Paleolithic, humans were frugivores (fruit eaters), who supplemented their meals with carrion, eggs, and small prey such as baby birds and mussels, and, only on rare occasions, managed to kill and consume big game such as antelopes.[93] This view is supported by the studies of higher apes, particularly chimpanzees. Chimpanzees are closest to humans genetically, sharing more than 96% of their DNA code with humans, and their digestive tract is functionally very similar to that of humans.[94] Chimpanzees are primarily frugivores, but they could and would consume and digest animal flesh, given the opportunity. In general, their actual diet in the wild is about 95% plant-based, with the remaining 5% filled with insects, eggs, and baby animals.[95][96] However, in some ecosystems chimpanzees are predatory, forming parties to hunt monkeys. [97] Some comparative studies of human and higher primate digestive tracts do suggest that humans have evolved to obtain greater amounts of calories from sources such as animal foods, allowing them to shrink the size of the gastrointestinal tract, relative to body mass, and to increase the brain mass instead.[82][98]
A difficulty with the frugivore point of view is that humans are established to conditionally require certain long-chain polyunsaturated fatty acids (LC-PUFAs), such as AA and DHA, from the diet.[99] Human LC-PUFA requirements are much greater than chimpanzees' because of humans' larger brain mass, and humans' abilities to synthesize them from other nutrients are poor, suggesting readily available external sources.[100] Pregnant and lactating females require 100 mg of DHA per day.[101] But LC-PUFAs are almost nonexistent in plants and in most tissues of warm-climate animals.
The main sources of DHA in the modern human diet are fish and the fatty organs of animals, such as brains, eyes and viscera. Microalgae is a farmed plant-based source commonly used by vegetarians. Despite the general shortage of evidence for extensive fishing, thought to require relatively sophisticated tools which have become available only in the last 30–50 thousand years, it has been argued that exploitation of coastal fauna somehow provided hominids with abundant LC-PUFAs.[100] Alternatively, it has been proposed that early hominids frequently scavenged predators' kills and consumed parts which were left untouched by predators, most commonly the brain, which is very high in AA and DHA.[101] Just 100 g of scavenged African ruminant brain matter provide more DHA than is consumed by a typical modern U.S. adult in the course of a week.[101][102] Other authors suggested that human ability to convert alpha-Linolenic acid into DHA, while poor, is, nevertheless, adequate to prevent DHA deficiency in a plant-based diet.[103]
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Nutritional factors and health effects[edit]

Fruits and vegetables, rich in vitamins, potassium and fiber, represent an important feature of forager diets.[49]
Since the end of the Paleolithic period, several foods that humans rarely or never consumed during previous stages of their evolution have been introduced as staples in their diet.[49] With the advent of agriculture and the beginning of animal domestication roughly 10,000 years ago, during the Neolithic Revolution, humans started consuming large amounts of dairy products, beans, cereals, alcohol and salt.[49] In the late 18th and early 19th centuries, the Industrial revolution led to the large scale development of mechanized food processing techniques and intensive livestock farming methods, that enabled the production of refined cereals, refined sugars and refined vegetable oils, as well as fattier domestic meats, which have become major components of Western diets.[49]
Such food staples have fundamentally altered several key nutritional characteristics of the human diet since the Paleolithic era, including glycemic load, fatty acid composition, macronutrient composition, micronutrient density, acid-base balance,sodium-potassium ratio, and fiber content.[49]
These dietary compositional changes have been theorized as risk factors in the pathogenesis of many of the so-called "diseases of civilization" and other chronic illnesses that are widely prevalent in Western societies,[2][49][104][105][106][107] includingobesity,[108][109][110] cardiovascular disease,[111][112][113] high blood pressure,[114] type 2 diabetes,[115][116] osteoporosis,[117][118] autoimmune diseases,[119] colorectal cancer,[120][121][122] myopia,[123] acne,[124][125][126][127] depression,[128] anddiseases related to vitamin and mineral deficiencies.[119][129][130][131]
Macronutrient composition[edit]
Protein and carbohydrates[edit]
"The increased contribution of carbohydrate from grains to the human diet following the agricultural revolution has effectively diluted the protein content of the human diet."[132] In modern forager diets, dietary protein is characteristically elevated (19–35% of energy) at the expense of carbohydrate (22–40% of energy).[58][59][133] High-protein diets may have a cardiovascular protective effect and may represent an effective weight loss strategy for the overweight or obese.[49] Furthermore,carbohydrate restriction may help prevent obesity and type 2 diabetes,[134][135] as well as atherosclerosis.[113] Carbohydrate deprivation to the point of ketosis has been argued both to have negative[136] and positive effects on health.[137][138]

Seeds such as walnuts are rich sources of protein and micronutrients
The notion that preagricultural foragers would have typically consumed a diet relatively low in carbohydrate and high in protein has been questioned.[139] Critics argue that there is insufficient data to identify the relative proportions of plant and animal foods consumed on average by Paleolithic humans in general,[9][10][79][140] and they stress the rich variety of ancient and modern forager diets.[10][71][72]Furthermore, substantial evidence exists suggesting many preagricultural foraging societies may have routinely consumed large quantities of carbohydrates in the form of carbohydrate-rich tubers (plant underground storage organs).[7][71][72]According to Staffan Lindeberg, an advocate of the Paleolithic diet, a plant-based diet rich in carbohydrates is consistent with the human evolutionary past.[1][2]
It has also been argued that relative freedom from degenerative diseases was, and still is, characteristic of all forager societies irrespective of the macronutrient characteristics of their diets.[141][142][143] Marion Nestle, a professor in the Department of Nutrition and Food Studies at New York University, judging from research relating nutritional factors to chronic disease risks and to observations of exceptionally low chronic disease rates among people eating Asian, Mediterranean, and vegetariandiets, has suggested that plant-based diets may be most associated with health and longevity.[8][140]
Fatty acids[edit]
Forager diets have been argued to maintain relatively high levels of monounsaturated and polyunsaturated fats, moderate levels of saturated fats (10–15% of total food energy[144]) as well as a low omega-6:omega-3 fatty acid ratio.[49][59][145] Cows fed a grass-based diet produce significant amounts of omega-3 fatty acids compared to grain-fed animals, while minimizing trans fats and saturated fats.[146] This high ratio of polyunsaturated to saturated fats has been challenged. While a low saturated fat intake was argued for[59] it has been argued that foragers would selectively hunt fatter animals and utilise the fattiest parts of the animals (such as bone marrow).[147]
Energy density[edit]
The Paleolithic diet has lower energy density than the typical diet consumed by modern humans.[148] This is especially true in primarily plant-based/vegetarian versions of the diet, but it still holds if substantial amounts of meat are included in calculations. For example, most fruits and berries contain 0.4 to 0.8 calories per gram, vegetables can be even lower than that (cucumbers contain only 0.16 calories per gram).[149] Game meat, such as cooked wild rabbit, is more energy-dense (up to 1.7 calories per gram), but it does not constitute the bulk of the diet by mass/volume at the recommended plant/animal ratios, and it does not reach the densities of many processed foods commonly consumed by modern humans: most McDonalds sandwiches such as the Big Mac average 2.4 to 2.8 calories/gram,[150] and sweets such as cookies and chocolate bars commonly exceed 4 calories/gram.
Low caloric density diets tend to provide a greater satiety feeling at the same energy intake, and they have been shown effective at achieving weight loss in overweight individuals without explicit caloric restrictions.[151][152][153]
Even some authors who may otherwise appear to be critical of the concept of Paleolithic diet have argued that high energy density of modern diets, as compared to ancestral/primate diets, contributes to the incidence of diseases of affluence in the industrial world.[83]
Micronutrient density[edit]

Fish and seafood, such as salmon, are significant sources of essential micronutrients
Fruits, vegetables, meat and organ meats, and seafood, which are staples of the forager diet, are more micronutrient-dense than refined sugars, grains, vegetable oils, and dairy products in relation to digestible energy. Consequently, the vitamin and mineral content of the diet is very high compared with a standard diet, in many cases a multiple of the RDA.[citation needed] Fish and seafood represent a particularly rich source of omega-3 fatty acids and other micronutrients, such as iodine, iron,zinc, copper, and selenium, that are crucial for proper brain function and development.[129] Terrestrial animal foods, such as muscle, brain, bone marrow, thyroid gland, and other organs, also represent a primary source of these nutrients.[54]Calcium-poor grains and legumes are excluded from the diet. Although, leafy greens like Kale and dandelion greens as well as nuts such as almonds are very high sources of calcium. Also, components in plants make their low calcium amounts much more easily absorbed, unlike items with high calcium content such as dairy[154][155][156][157] Two notable exceptions are calcium (see below) and vitamin D, both of which may be present in the diet in inadequate quantities. Modern humans require much more vitamin D than foragers, because they do not get the same amount of exposure to sun. This need is commonly satisfied in developed countries by artificially fortifying dairy products with the vitamin. To avoid deficiency, a modern human on a forager diet would have to take artificial supplements of the vitamin, ensure adequate intake of some fatty fish,[158] or increase the amount of exposure to sunlight (it has been estimated that 30 minutes of exposure to mid-day sun twice a week is adequate for most people).[159]
Fiber content and glycemic load[edit]
Despite its relatively low carbohydrate content, the Paleolithic diet involves a substantial increase in consumption of fruit and vegetables, compared to the Western diet, potentially as high as 1.65 to 1.9 kg/day.[160] Forager diets, which rely on uncultivated, heavily fibrous fruit and vegetables, contain even more. Fiber intake in preagricultural diets is thought to have exceeded 100 g/day.[60] This is dramatically higher than the actual current U.S. intake of 15 g/day.[60]

Fiber-rich root vegetables, such asbeets, rutabagas, carrots, celeriac andturnips, maintain nutrient properties (lowglycemic and insulin responses) characteristic of traditional forager plant foods.[citation needed]
Unrefined wild plant foods like those available to contemporary foragers typically exhibit low glycemic indices.[161] Moreover, dairy products, such as milk, have low glycemic indices, but are highly insulinotropic, with an insulin index similar to that of white bread.[162][163] However, in fermented milk products, such as yogurt, the presence of organic acids may counteract the insulinotropic effect of milk in mixed meals.[164] These dietary characteristics may lower risk of diabetes, obesity and other related metabolic syndrome diseases by placing less stress on the pancreas to produce insulin due to staggered absorption of glucose, thus preventing insulin insensitivity.[165]
Sodium-potassium ratio[edit]
It has been estimated that people in the Paleolithic era consumed 11,000 mg of potassium and 700 mg of sodium daily.[20]
The dominance of sodium over potassium in the U.S. diet adversely affects cardiovascular function and contributes to hypertension and stroke:[118][166] the Paleolithic diet inverts this ratio.
Calcium and acid-base balance[edit]
Diets containing high amounts of animal products, animal protein, processed foods, and other foods that induce and sustain increased acidity of body fluid may contribute to the development of osteoporosis and renal stones, loss of muscle mass, and age-related renal insufficiency due to the body's use of calcium to buffer pH.[167][168] The paleo diet may not contain the high levels of calcium recommended in the U.S. to prevent these effects.[169] However, because of the absence of cereals and energy-dense, nutrient-poor foods in the ancestral forager diet—foods that displace base-yielding fruits and vegetables—that diet has been estimated to produce a net base load on the body, as opposed to a net acid load,[117] which may reduce calcium excretion.[170]
Bioactive substances and antinutrients[edit]
Furthermore, cereal grains, legumes and milk contain bioactive substances, such as gluten and casein, which have been implicated in the development of various health problems.[2] Consumption of gluten, a component of certain grains, such as wheat, rye and barley, is known to have adverse health effects in individuals suffering from a range of gluten sensitivities, including celiac disease. Since the Paleolithic diet is devoid of cereal grains, it is free of gluten. The paleo diet is also casein-free. Casein, a protein found in milk and dairy products, may impair glucose tolerance in humans.[2]
Compared to Paleolithic food groups, cereal grains and legumes contain high amounts of antinutrients, including alkylresorcinols, alpha-amylase inhibitors, protease inhibitors, lectins and phytates, substances known to interfere with the body's absorption of many key nutrients.[2][105][119]Molecular-mimicking proteins, which are basically made up of strings of amino acids that closely resemble those of another totally different protein, are also found in grains and legumes, as well as milk and dairy products.[2][105][119] Advocates of the Paleolithic diet have argued that these components of agrarian diets promote vitamin and mineral deficiencies and may explain the development of the "diseases of civilization" as well as a number of autoimmune-related diseases.[2][105][119]
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Variations[edit]
Other forms of the diet either exclude fruits or include fruits. Some variants also include dairy products or legumes.[citation needed]
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Research[edit]
Archeological record[edit]
One line of evidence used to support the Paleolithic diet is the decline in human health and body mass purported to have occurred with the adoption of agriculture, at the end of the Paleolithic era.[71][119] Studies have suggested that with the introduction of domesticated and processed plant foods, such as cereal grains, in the human diet, there was, in many areas, a general decrease in body stature and dentition size, and an increase in dental caries rates. While a general decline in health apparently followed the introduction of agriculture in some areas, it is unclear to what degree this change is related solely or at all to dietary patterns, since, as scholars have pointed out, other factors such as increased sedentism, different work habits, greater general caloric scarcity, and denser settlement patterns and concomitant disease transmission may also have played important roles.[9][171][172] Evidence for the effect of the switch to agriculture on general life expectancy is mixed, with some populations exhibiting an apparent decrease in life expectancy and others an apparent increase.[173]
Observational studies[edit]
Based on the subsistence patterns and biomarkers of foragers studied in the last century, advocates argue that modern humans are well adapted to the diet of their Paleolithic ancestor.[174] The diet of modern forager groups is believed to be representative of patterns for humans of fifty to twenty-five thousand years ago,[174] and individuals from these and other technologically primitive societies,[175][176] including those individuals who reach the age of 60 or beyond,[27][177] seem to be largely free of the signs and symptoms of chronic disease (such as obesity, high blood pressure, nonobstructive coronary atherosclerosis, and insulin resistance) that universally afflict the elderly in western societies (with the exception of osteoarthritis, which afflicts both populations).[2][4][174] Moreover, when these people adopt western diets, their health declines and they begin to exhibit signs and symptoms of "diseases of civilization".[3][174] In one clinical study, stroke and ischaemic heart disease appeared to be absent in a population living on the island of Kitava, in Papua New Guinea, where a subsistence lifestyle, uninfluenced by western dietary habits, was still maintained.[27][178]
One of the most frequent criticisms of the Paleolithic diet is that it is unlikely that preagricultural foragers suffered from the diseases of modern civilization simply because they did not live long enough to develop these illnesses, which are typically associated with old age.[4][7][179][180][181]According to S. Jay Olshansky and Bruce Carnes, "there is neither convincing evidence nor scientific logic to support the claim that adherence to a Paleolithic diet provides a longevity benefit."[181] In response to this argument, advocates of the paleodiet state that while Paleolithic foragers did have a short average life expectancy, modern human populations with lifestyles resembling that of our preagricultural ancestors have little or no diseases of affluence, despite sufficient numbers of elderly.[4][182] In forager societies where demographic data is available, the elderly are present, but they tend to have high mortality rates and rarely survive past the age of 80, with causes of death (when known) ranging from injuries to measles and tuberculosis.[183]
Critics further contend that food energy excess, rather than the consumption of specific novel foods, such as grains and dairy products, underlies the diseases of affluence.[7][71][184] According to Geoffrey Cannon,[7] science and health policy advisor to the World Cancer Research Fund, humans are designed to work hard physically to produce food for subsistence and to survive periods of acute food shortage, and are not adapted to a diet rich in energy-dense foods.[185] Similarly, William R. Leonard, a professor of anthropology at Northwestern University, states that the health problems facing industrial societies stem not from deviations from a specific ancestral diet but from an imbalance between calories consumed and calories burned, a state of energy excess uncharacteristic of ancestral lifestyles.[184]
Intervention studies[edit]
The first animal experiment on a Paleolithic diet suggested that this diet, as compared with a cereal-based diet, conferred higher insulin sensitivity, lower C-reactive protein and lower blood pressure in 24 domestic pigs.[186] There was no difference in basal serum glucose.[186] The first human clinical randomized controlled trial involved 29 people with glucose intolerance and ischemic heart disease, and it found that those on a Paleolithic diet had a greater improvement in glucose tolerance compared to those on a Mediterranean diet.[5][187] Furthermore, the Paleolithic diet was found to be more satiating per calorie compared to the Mediterranean diet.[188]
A clinical, randomized, controlled cross-over study in the primary care setting compared the Paleolithic diet with a commonly prescribed diet for type 2 diabetes. The Paleolithic diet resulted in lower mean values of HbA1c, triacylglycerol, diastolic blood pressure, body mass index, waist circumference and higher values of high density lipoprotein when compared to the Diabetes diet. Also, glycemic control and other cardiovascular factors were improved in both diets without significant differences. It is also important to note that the Paleolithic diet was lower in total energy, energy density, carbohydrate, dietary glycemic load and glycemic index, saturated fatty acids and calcium, but higher in unsaturated fatty acids, dietary cholesterol and some vitamins.[189] Two clinical trials designed to test various physiological effects of the Paleolithic diet are currently underway,[190][191] and the results of one completed trial[192] have shown metabolic and physiologic improvements.[6] The European Journal of Clinical Nutrition published a study[193] of a trial of the Paleolithic diet in 20 healthy volunteers. The study had no control group, and only 14 individuals completed the diet. In the study, in three weeks there was an average weight reduction of 2.3 kg, an average reduction in waist circumference of 1.5 cm (about one-half inch), an average reduction in systolic blood pressure of 3 mm Hg, and a 72% reduction in plasminogen activator inhibitor-1 (which might translate into a reduced risk of heart attack and stroke.) However, the NHS Knowledge Service pointed out that this study, like most human diet studies, relied on observational data. The NHS concluded that the lack of a control group, and the small sample of size of the study, compromises their conclusions. With only 14 participants the study lacks the statistical power to detect health improvements, and perhaps the simple fact that these 14 individuals knew that they were on a diet program made them more aware of weight and exercise regime, skewing the results.[194]
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Reception[edit]
Critics have argued that to the extent that foraging societies fail to suffer from "diseases of civilization", this may be due to reduced calories in their diet, shorter average lifespans, or a variety of other factors, rather than dietary composition.[141] Some researchers have also taken issue with the accuracy of the diet's underlying evolutionary logic or suggested that the diet could potentially pose health risks.[71][72][140][141]
A 2011 ranking by U.S. News & World Report, involving a panel of 22 experts, ranked the Paleo diet lowest of the 20 diets evaluated based on factors including health, weight-loss and ease of following.[195] These results were repeated in the 2012 survey, in which the diet tied with the Dukan diet for the lowest ranking out of 29 diets; U.S. News stated that their experts "took issue with the diet on every measure".[195] In the 2013 rankings, the Paleo diet tied for last place out of 29, and in 2014, it tied for last out of 32. However, one expert involved in the ranking stated that a "true Paleo diet might be a great option: very lean, pure meats, lots of wild plants. The modern approximations… are far from it."[195] He added that "duplicating such a regimen in modern times would be difficult."[195]
The U.S. News ranking assumed a low-carb version of the paleo diet, specifically containing only 23% carbohydrates.[196] Higher carbohydrate versions of the paleo diet, which allow for significant consumption of root vegetables,[197] were not a part of this ranking.[195] Dr. Loren Cordain, a proponent of a low-carbohydrate Paleolithic diet, responded to the U.S. News ranking, stating that their "conclusions are erroneous and misleading" and pointing out that "five studies, four since 2007, have experimentally tested contemporary versions of ancestral human diets and have found them to be superior to Mediterranean diets, diabetic diets and typical western diets in regard to weight loss, cardiovascular disease risk factors and risk factors for type 2 diabetes."[63][64][198] The editors of the U.S. News ranking replied that they had reviewed the five studies and found them to be "small and short, making strong conclusions difficult".[64]

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History[edit]
First popularized in the mid-1970s by gastroenterologist Walter L. Voegtlin,[12][13] it has been promoted and adapted by a number of authors and researchers in several books and academic journals.[9] A common theme in evolutionary medicine,[14][15] Gastroenterologist Walter L. Voegtlin was one of the first to suggest that following a diet similar to that of the Paleolithic era would improve a person's health.[13] In 1975, he self-published The Stone Age Diet: Based on In-depth Studies of Human Ecology and the Diet of Man,[12] in which he argued that humans are carnivorous animals. He noted that the ancestral Paleolithic diet was that of a carnivore — chiefly fats and protein, with small amounts of carbohydrates.[16][17] His dietary prescriptions were based on his own medical treatments of various digestive problems, namely colitis, Crohn's disease, irritable bowel syndrome and indigestion.[18][19]
In 1985, S. Boyd Eaton and Melvin Konner published a paper on Paleolithic nutrition in the New England Journal of Medicine,[20] which attracted wider mainstream medical attention to the concept.[21] Three years later, Eaton, Konner, and Marjorie Shostak published a book about this nutritional approach,[22] which was based on achieving the same proportions of nutrients (fat, protein, carbohydrates, vitamins, and minerals) as were present in the diets of late Paleolithic people. It did not exclude foods that were not available before the development of agriculture. As such, this nutritional approach included skimmed milk, whole-grain bread, brown rice, and potatoes prepared without fat, on the premise that such foods supported a diet with the same macronutrient composition as the Paleolithic diet.[16][23][24] In 1989, these authors published a second book on Paleolithic nutrition.[25][26]
Starting in 1989, Staffan Lindeberg led scientific surveys of the non-westernized population on Kitava, one of the Trobriand Islands of Papua New Guinea. These surveys, collectively referred to as the Kitava Study, found that this population apparently did not suffer from diabetes, hypertension,ischemic heart disease, obesity, or strokes. Starting with the first publication in 1993,[27] scholars with the Kitava Study have published a number of scientific works on the relationship between diet and western disease.[28] In 2003, Lindeberg published a Swedish-language medical textbook on the subject.[29] In 2010, this book was wholly revised, updated, translated and published for the first time in English.[30]
Since the end of the 1990s, a number of medical doctors and nutritionists[31][32][33] have advocated a return to a so-called Paleolithic (preagricultural) diet.[9] Proponents of this nutritional approach have published books[34][35][36] and created websites[37][38][39][40] to promote their dietary prescriptions.[41][42][43][44][45] They have synthesized diets from modern foods that emulate nutritional characteristics of the ancient Paleolithic diet. Some of these allow specific foods that would have been unavailable to pre-agricultural peoples, such as some animal products (i.e., dairy), processed oils, and beverages.[34][46][47]
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Practices[edit]

Raw Paleolithic-style dish: sashimi (raw fish) dinner set
The Paleolithic diet seeks to mimic the diet of preagricultural foragers; it generally corresponds to what was available in any of the ecological niches of Paleolithic humans.[1][2] Based upon commonly available modern foods, it includes cultivatedplants and domesticated animal meat as an alternative to the wild sources of the original pre-agricultural diet.[1][48] The ancestral human diet is inferred from historical and ethnographic studies of modern-day forages as well as archaeological finds,anthropological evidence and application of optimal foraging theory.[49][50][51][52]
The Paleolithic diet consists of foods that can be fished and hunted, such as seafood and meat (including offal), and foods that can be gathered, such as eggs, fruits, herbs, insects, mushrooms, nuts, seeds, spices, and vegetables.[1] The meats recommended for consumption are preferably free of food additives, such as wild game meats and grass-fed beef, since they contain higher levels of omega-3 fats compared with grain-produced domestic meats.[1][48][53] Food groups that advocates claim were rarely or never consumed by humans before the Neolithic agricultural revolution are excluded from the diet, mainly dairy products, grains, legumes (e.g., beans and peanuts), processed oils, refined sugar, and salt.[1] Many of these foods would have been available at certain times of the year, and may or may not have been consumed. Some advocates consider the use of oils with low omega-6/omega-3 ratios, such as olive oil, to be healthy and advisable.[48]

Paleolithic-style dish: roast pork with cooked and raw vegetables and fruit
On the Paleolithic diet, practitioners are permitted to drink mainly water, and some advocates recommend tea as a healthy drink.[48] Eating a wide variety of plant foods is recommended to avoid high intakes of potentially harmful bioactive substances, such as goitrogens, which are present in some roots, seeds, and vegetables.[1][50][54] Unlike raw food diets, all foods may be cooked, without restrictions.[1][55] But, there are Paleolithic dieters who believe that humans have not adapted to cooked foods, and so they eat only foods which are both raw and Paleolithic.[56][57]
According to certain proponents of the Paleolithic diet, practitioners should derive about 56–65% of their food energy from animal foods and 36–45% from plant foods. They recommend a diet high in protein(19–35% energy) and relatively low in carbohydrates (22–40% energy), with a fat intake (28–58% energy) similar to or higher than that found in Western diets.[48][58][59]
Staffan Lindeberg advocates a Paleolithic diet, but does not recommend any particular proportions of plants versus meat or macronutrient ratios.[1][50] According to Lindeberg, calcium supplementation may be considered when the intake of green leafy vegetables and other dietary sources of calcium is limited.[1]
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Rationale and evolutionary assumptions[edit]
According to S. Boyd Eaton, "we are the heirs of inherited characteristics accrued over millions of years; the vast majority of our biochemistry and physiology are tuned to life conditions that existed before the advent of agriculture some 10,000 years ago. Genetically our bodies are virtually the same as they were at the end of the Paleolithic era some 20,000 years ago."[60]
Therefore, an ideal diet for human health and well-being is one that resembles this ancestral diet.[2][49]
The reasoning underlying this nutritional approach is that natural selection had sufficient time to genetically adapt the metabolism and physiology of Paleolithic humans to the varying dietary conditions of that era. But in the 10,000 years since the invention of agriculture and its consequent major change in the human diet, natural selection has had too little time to make the optimal genetic adaptations to the new diet.[1][2] Physiological and metabolic maladaptations such as diabetes have been seen in Native Americans populations newly introduced to the contemporary Western diet.[61]
More than 70% of the total daily energy consumed by all people in the United States comes from foods such as alcohol, cereals, dairy products, refined sugars, and refined vegetable oils. Advocates of the Paleolithic diet assert these foods contributed little or none of the energy in the typical preagricultural hominin diet[49] and argue that excessive consumption of these novel Neolithic and industrial-era foods is responsible for the current epidemic levels of cancer, cardiovascular disease, high blood pressure, obesity, osteoporosis, and type 2 diabetes in the US and other contemporary Western populations.[49]
Supporters also point to several potentially therapeutic nutritional characteristics of preagricultural diets.[49][62][63][64]
Physical activity[edit]
Researchers have applied the evolutionary rationale to the paleolithic lifestyle to argue for high levels of physical activity in addition to dietary practices. They suggest that human genes "evolved with the expectation of requiring a certain threshold of physical activity", and the sedentary lifestyle results in abnormal gene expression.[65][66] Compared to ancestral humans, modern humans often have increased body fat and substantially less lean muscle, which is a risk factor for insulin resistance.[67] Human metabolic processes were evolved in the presence of physical activity–rest cycles, which regularly depleted skeletal muscles of their glycogen stores.[68] To date, it is unclear whether these activity cycles universally included prolonged endurance activity (e.g., persistence hunting) and/or shorter, higher intensity activity. S. Boyd Eaton estimated that ancestral humans spent one-third of their caloric intake on physical activity (1000 cal/day out of the total caloric intake of 3000 cal/day),[69] and that the paleolithic lifestyle was well approximated by the WHO recommendation of the physical activity level of 1.75, or 60 minutes/day of moderate-intensity exercise.[70] L. Cordain estimated that the optimal level of physical activity is on the order of 90 cal/kg/week (900 cal/day for a 70 kg human.)[66]
Opposing views[edit]
Critics have questioned the accuracy of the science on which the diet is based. John A. McDougall (M.D), author of The Starch Solution, attempted to discredit the science used to determine the Paleolithic diet, and proposed that the human diet around this time was instead based primarily on starches.[citation needed]
The evolutionary assumptions underlying the Paleolithic diet have been disputed.[10][23][71][72] According to Alexander Ströhle, Maike Wolters and Andreas Hahn, with the Department of Food Science at the University of Hanover, the statement that the human genome evolved during thePleistocene (a period from 1,808,000 to 11,550 years ago) rests on the gene-centered view of evolution, which they believe to be controversial.[72] They rely on Gray (2001)[73] to argue that evolution of organisms cannot be reduced to the genetic level with reference to mutation, and that there is no one-to-one relationship between genotype and phenotype.[72] They further question the notion that 10,000 years is an insufficient period of time to ensure an adequate adaptation to agrarian diets.[72] They note that alleles conferring lactose tolerance increased to high frequencies in Europe just a few thousand years after animal husbandry was invented. Recent increases in the number of copies of the gene for salivary amylase, which digests starch, appear to be related to the development of agriculture.[74] Referring to Wilson (1994),[75] Ströhle et al. argue that "the number of generations that a species existed in the old environment was irrelevant, and that the response to the change of the environment of a species would depend on the heritability of the traits, the intensity of selection and the number of generations that selection acts."[76] They state that if the diet of Neolithic agriculturalists had been in discordance with their physiology, then this would have created a selection pressure for evolutionary change. Modern humans, such as Europeans, whose ancestors have subsisted on agrarian diets for 400–500 generations, should be somehow adequately adapted to it. In response to this argument, Wolfgang Kopp states that "we have to take into account that death from atherosclerosis and cardiovascular disease (CVD) occurs later during life, as a rule after the reproduction phase. Even a high mortality from CVD after the reproduction phase will create little selection pressure. Thus, it seems that a diet can be functional (it keeps us going) and dysfunctional (it causes health problems) at the same time."[76] Moreover, S. Boyd Eaton and colleagues have indicated that "comparative genetic data provide compelling evidence against the contention that long exposure to agricultural and industrial circumstances has distanced us, genetically, from our Stone Age (sic) ancestors";[4] however, they mention exceptions such as increased lactose and gluten tolerance, which improve ability to digest dairy and grains, while other studies indicate that human adaptive evolution has accelerated since the Paleolithic.[77]
Referencing Mahner et al. (2001)[78] and Ströhle et al. (2006),[79] Ströhle et al. state that "whatever is the fact, to think that a dietary factor is valuable (functional) to the organism only when there was ‘genetical adaptation’ and hence a new dietary factor is dysfunctional per se because there was no evolutionary adaptation to it, such a panselectionist misreading of biological evolution seems to be inspired by a naive adaptationistic view of life."[72]
Katharine Milton, a professor of physical anthropology at the University of California, Berkeley, has also disputed the evolutionary logic upon which the Paleolithic diet is based. She questions the premise that the metabolism of modern humans must be genetically adapted to the dietary conditions of the Paleolithic.[10] Relying on several of her previous publications,[80][81][82][83] Milton states that "there is little evidence to suggest that human nutritional requirements or human digestive physiology were significantly affected by such diets at any point in human evolution."[10]
There is some evidence suggesting that Paleolithic societies were processing cereals for food use at least as early as 23,000 BCE. These findings are a matter of dispute.[84][85][86][87][88]
Plant-to-animal ratio[edit]
The specific plant to animal food ratio in the Paleolithic diet is also a matter of some dispute. The average diet among modern foraging societies is estimated to consist of 64–68% of animal calories and 32–36% of plant calories,[59][89] with animal calories further divided between fished and hunted animals in varying proportions (most typically, with hunted animal food comprising 26–35% of the overall diet). As part of the Man the Hunter paradigm, this ratio was used as the basis of the earliest forms of the Paleolithic diet by Voegtlin, Eaton and others. To this day, many advocates of the Paleolithic diet consider high percentage of animal flesh to be one of the key features of the diet.
However, great disparities do exist, even between different modern foraging societies. The animal-derived calorie percentage ranges from 25% in the Gwi people of southern Africa, to 99% in Alaskan Nunamiut.[90] The animal-derived percentage value is skewed upwards by hunting-oriented polar foraging societies, who have no choice but to eat animal food because of the inaccessibility of plant foods. Since those environments were only populated relatively recently (for example, Paleo-Indian ancestors of Nunamiut are thought to have arrived in Alaska no earlier than 30,000 years ago), such diets represent recent adaptations rather than conditions that shaped human evolution during much of the Paleolithic. More generally, hunting and fishing tend to provide a higher percentage of energy in forager societies living at higher latitudes. Excluding cold-climate and equestrian foragers results in a diet structure of 52% plant calories, 26% hunting calories, and 22% fishing calories.[89] Furthermore, those numbers may still not be representative of a typical Paleolithic diet, since fishing did not become common in many parts of the world until the Upper Paleolithic period 35-40 thousand years ago,[91] and early humans' hunting abilities were relatively limited,[dubious – discuss] compared to modern foragers, as well (the oldest incontrovertible evidence for the existence of bows only dates to about 8000 BCE,[92] and nets and traps were invented 20,000 to 29,000 years ago).
Another view is that, up until the Upper Paleolithic, humans were frugivores (fruit eaters), who supplemented their meals with carrion, eggs, and small prey such as baby birds and mussels, and, only on rare occasions, managed to kill and consume big game such as antelopes.[93] This view is supported by the studies of higher apes, particularly chimpanzees. Chimpanzees are closest to humans genetically, sharing more than 96% of their DNA code with humans, and their digestive tract is functionally very similar to that of humans.[94] Chimpanzees are primarily frugivores, but they could and would consume and digest animal flesh, given the opportunity. In general, their actual diet in the wild is about 95% plant-based, with the remaining 5% filled with insects, eggs, and baby animals.[95][96] However, in some ecosystems chimpanzees are predatory, forming parties to hunt monkeys. [97] Some comparative studies of human and higher primate digestive tracts do suggest that humans have evolved to obtain greater amounts of calories from sources such as animal foods, allowing them to shrink the size of the gastrointestinal tract, relative to body mass, and to increase the brain mass instead.[82][98]
A difficulty with the frugivore point of view is that humans are established to conditionally require certain long-chain polyunsaturated fatty acids (LC-PUFAs), such as AA and DHA, from the diet.[99] Human LC-PUFA requirements are much greater than chimpanzees' because of humans' larger brain mass, and humans' abilities to synthesize them from other nutrients are poor, suggesting readily available external sources.[100] Pregnant and lactating females require 100 mg of DHA per day.[101] But LC-PUFAs are almost nonexistent in plants and in most tissues of warm-climate animals.
The main sources of DHA in the modern human diet are fish and the fatty organs of animals, such as brains, eyes and viscera. Microalgae is a farmed plant-based source commonly used by vegetarians. Despite the general shortage of evidence for extensive fishing, thought to require relatively sophisticated tools which have become available only in the last 30–50 thousand years, it has been argued that exploitation of coastal fauna somehow provided hominids with abundant LC-PUFAs.[100] Alternatively, it has been proposed that early hominids frequently scavenged predators' kills and consumed parts which were left untouched by predators, most commonly the brain, which is very high in AA and DHA.[101] Just 100 g of scavenged African ruminant brain matter provide more DHA than is consumed by a typical modern U.S. adult in the course of a week.[101][102] Other authors suggested that human ability to convert alpha-Linolenic acid into DHA, while poor, is, nevertheless, adequate to prevent DHA deficiency in a plant-based diet.[103]
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Nutritional factors and health effects[edit]

Fruits and vegetables, rich in vitamins, potassium and fiber, represent an important feature of forager diets.[49]
Since the end of the Paleolithic period, several foods that humans rarely or never consumed during previous stages of their evolution have been introduced as staples in their diet.[49] With the advent of agriculture and the beginning of animal domestication roughly 10,000 years ago, during the Neolithic Revolution, humans started consuming large amounts of dairy products, beans, cereals, alcohol and salt.[49] In the late 18th and early 19th centuries, the Industrial revolution led to the large scale development of mechanized food processing techniques and intensive livestock farming methods, that enabled the production of refined cereals, refined sugars and refined vegetable oils, as well as fattier domestic meats, which have become major components of Western diets.[49]
Such food staples have fundamentally altered several key nutritional characteristics of the human diet since the Paleolithic era, including glycemic load, fatty acid composition, macronutrient composition, micronutrient density, acid-base balance,sodium-potassium ratio, and fiber content.[49]
These dietary compositional changes have been theorized as risk factors in the pathogenesis of many of the so-called "diseases of civilization" and other chronic illnesses that are widely prevalent in Western societies,[2][49][104][105][106][107] includingobesity,[108][109][110] cardiovascular disease,[111][112][113] high blood pressure,[114] type 2 diabetes,[115][116] osteoporosis,[117][118] autoimmune diseases,[119] colorectal cancer,[120][121][122] myopia,[123] acne,[124][125][126][127] depression,[128] anddiseases related to vitamin and mineral deficiencies.[119][129][130][131]
Macronutrient composition[edit]
Protein and carbohydrates[edit]
"The increased contribution of carbohydrate from grains to the human diet following the agricultural revolution has effectively diluted the protein content of the human diet."[132] In modern forager diets, dietary protein is characteristically elevated (19–35% of energy) at the expense of carbohydrate (22–40% of energy).[58][59][133] High-protein diets may have a cardiovascular protective effect and may represent an effective weight loss strategy for the overweight or obese.[49] Furthermore,carbohydrate restriction may help prevent obesity and type 2 diabetes,[134][135] as well as atherosclerosis.[113] Carbohydrate deprivation to the point of ketosis has been argued both to have negative[136] and positive effects on health.[137][138]

Seeds such as walnuts are rich sources of protein and micronutrients
The notion that preagricultural foragers would have typically consumed a diet relatively low in carbohydrate and high in protein has been questioned.[139] Critics argue that there is insufficient data to identify the relative proportions of plant and animal foods consumed on average by Paleolithic humans in general,[9][10][79][140] and they stress the rich variety of ancient and modern forager diets.[10][71][72]Furthermore, substantial evidence exists suggesting many preagricultural foraging societies may have routinely consumed large quantities of carbohydrates in the form of carbohydrate-rich tubers (plant underground storage organs).[7][71][72]According to Staffan Lindeberg, an advocate of the Paleolithic diet, a plant-based diet rich in carbohydrates is consistent with the human evolutionary past.[1][2]
It has also been argued that relative freedom from degenerative diseases was, and still is, characteristic of all forager societies irrespective of the macronutrient characteristics of their diets.[141][142][143] Marion Nestle, a professor in the Department of Nutrition and Food Studies at New York University, judging from research relating nutritional factors to chronic disease risks and to observations of exceptionally low chronic disease rates among people eating Asian, Mediterranean, and vegetariandiets, has suggested that plant-based diets may be most associated with health and longevity.[8][140]
Fatty acids[edit]
Forager diets have been argued to maintain relatively high levels of monounsaturated and polyunsaturated fats, moderate levels of saturated fats (10–15% of total food energy[144]) as well as a low omega-6:omega-3 fatty acid ratio.[49][59][145] Cows fed a grass-based diet produce significant amounts of omega-3 fatty acids compared to grain-fed animals, while minimizing trans fats and saturated fats.[146] This high ratio of polyunsaturated to saturated fats has been challenged. While a low saturated fat intake was argued for[59] it has been argued that foragers would selectively hunt fatter animals and utilise the fattiest parts of the animals (such as bone marrow).[147]
Energy density[edit]
The Paleolithic diet has lower energy density than the typical diet consumed by modern humans.[148] This is especially true in primarily plant-based/vegetarian versions of the diet, but it still holds if substantial amounts of meat are included in calculations. For example, most fruits and berries contain 0.4 to 0.8 calories per gram, vegetables can be even lower than that (cucumbers contain only 0.16 calories per gram).[149] Game meat, such as cooked wild rabbit, is more energy-dense (up to 1.7 calories per gram), but it does not constitute the bulk of the diet by mass/volume at the recommended plant/animal ratios, and it does not reach the densities of many processed foods commonly consumed by modern humans: most McDonalds sandwiches such as the Big Mac average 2.4 to 2.8 calories/gram,[150] and sweets such as cookies and chocolate bars commonly exceed 4 calories/gram.
Low caloric density diets tend to provide a greater satiety feeling at the same energy intake, and they have been shown effective at achieving weight loss in overweight individuals without explicit caloric restrictions.[151][152][153]
Even some authors who may otherwise appear to be critical of the concept of Paleolithic diet have argued that high energy density of modern diets, as compared to ancestral/primate diets, contributes to the incidence of diseases of affluence in the industrial world.[83]
Micronutrient density[edit]

Fish and seafood, such as salmon, are significant sources of essential micronutrients
Fruits, vegetables, meat and organ meats, and seafood, which are staples of the forager diet, are more micronutrient-dense than refined sugars, grains, vegetable oils, and dairy products in relation to digestible energy. Consequently, the vitamin and mineral content of the diet is very high compared with a standard diet, in many cases a multiple of the RDA.[citation needed] Fish and seafood represent a particularly rich source of omega-3 fatty acids and other micronutrients, such as iodine, iron,zinc, copper, and selenium, that are crucial for proper brain function and development.[129] Terrestrial animal foods, such as muscle, brain, bone marrow, thyroid gland, and other organs, also represent a primary source of these nutrients.[54]Calcium-poor grains and legumes are excluded from the diet. Although, leafy greens like Kale and dandelion greens as well as nuts such as almonds are very high sources of calcium. Also, components in plants make their low calcium amounts much more easily absorbed, unlike items with high calcium content such as dairy[154][155][156][157] Two notable exceptions are calcium (see below) and vitamin D, both of which may be present in the diet in inadequate quantities. Modern humans require much more vitamin D than foragers, because they do not get the same amount of exposure to sun. This need is commonly satisfied in developed countries by artificially fortifying dairy products with the vitamin. To avoid deficiency, a modern human on a forager diet would have to take artificial supplements of the vitamin, ensure adequate intake of some fatty fish,[158] or increase the amount of exposure to sunlight (it has been estimated that 30 minutes of exposure to mid-day sun twice a week is adequate for most people).[159]
Fiber content and glycemic load[edit]
Despite its relatively low carbohydrate content, the Paleolithic diet involves a substantial increase in consumption of fruit and vegetables, compared to the Western diet, potentially as high as 1.65 to 1.9 kg/day.[160] Forager diets, which rely on uncultivated, heavily fibrous fruit and vegetables, contain even more. Fiber intake in preagricultural diets is thought to have exceeded 100 g/day.[60] This is dramatically higher than the actual current U.S. intake of 15 g/day.[60]

Fiber-rich root vegetables, such asbeets, rutabagas, carrots, celeriac andturnips, maintain nutrient properties (lowglycemic and insulin responses) characteristic of traditional forager plant foods.[citation needed]
Unrefined wild plant foods like those available to contemporary foragers typically exhibit low glycemic indices.[161] Moreover, dairy products, such as milk, have low glycemic indices, but are highly insulinotropic, with an insulin index similar to that of white bread.[162][163] However, in fermented milk products, such as yogurt, the presence of organic acids may counteract the insulinotropic effect of milk in mixed meals.[164] These dietary characteristics may lower risk of diabetes, obesity and other related metabolic syndrome diseases by placing less stress on the pancreas to produce insulin due to staggered absorption of glucose, thus preventing insulin insensitivity.[165]
Sodium-potassium ratio[edit]
It has been estimated that people in the Paleolithic era consumed 11,000 mg of potassium and 700 mg of sodium daily.[20]
The dominance of sodium over potassium in the U.S. diet adversely affects cardiovascular function and contributes to hypertension and stroke:[118][166] the Paleolithic diet inverts this ratio.
Calcium and acid-base balance[edit]
Diets containing high amounts of animal products, animal protein, processed foods, and other foods that induce and sustain increased acidity of body fluid may contribute to the development of osteoporosis and renal stones, loss of muscle mass, and age-related renal insufficiency due to the body's use of calcium to buffer pH.[167][168] The paleo diet may not contain the high levels of calcium recommended in the U.S. to prevent these effects.[169] However, because of the absence of cereals and energy-dense, nutrient-poor foods in the ancestral forager diet—foods that displace base-yielding fruits and vegetables—that diet has been estimated to produce a net base load on the body, as opposed to a net acid load,[117] which may reduce calcium excretion.[170]
Bioactive substances and antinutrients[edit]
Furthermore, cereal grains, legumes and milk contain bioactive substances, such as gluten and casein, which have been implicated in the development of various health problems.[2] Consumption of gluten, a component of certain grains, such as wheat, rye and barley, is known to have adverse health effects in individuals suffering from a range of gluten sensitivities, including celiac disease. Since the Paleolithic diet is devoid of cereal grains, it is free of gluten. The paleo diet is also casein-free. Casein, a protein found in milk and dairy products, may impair glucose tolerance in humans.[2]
Compared to Paleolithic food groups, cereal grains and legumes contain high amounts of antinutrients, including alkylresorcinols, alpha-amylase inhibitors, protease inhibitors, lectins and phytates, substances known to interfere with the body's absorption of many key nutrients.[2][105][119]Molecular-mimicking proteins, which are basically made up of strings of amino acids that closely resemble those of another totally different protein, are also found in grains and legumes, as well as milk and dairy products.[2][105][119] Advocates of the Paleolithic diet have argued that these components of agrarian diets promote vitamin and mineral deficiencies and may explain the development of the "diseases of civilization" as well as a number of autoimmune-related diseases.[2][105][119]
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Variations[edit]
Other forms of the diet either exclude fruits or include fruits. Some variants also include dairy products or legumes.[citation needed]
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Research[edit]
Archeological record[edit]
One line of evidence used to support the Paleolithic diet is the decline in human health and body mass purported to have occurred with the adoption of agriculture, at the end of the Paleolithic era.[71][119] Studies have suggested that with the introduction of domesticated and processed plant foods, such as cereal grains, in the human diet, there was, in many areas, a general decrease in body stature and dentition size, and an increase in dental caries rates. While a general decline in health apparently followed the introduction of agriculture in some areas, it is unclear to what degree this change is related solely or at all to dietary patterns, since, as scholars have pointed out, other factors such as increased sedentism, different work habits, greater general caloric scarcity, and denser settlement patterns and concomitant disease transmission may also have played important roles.[9][171][172] Evidence for the effect of the switch to agriculture on general life expectancy is mixed, with some populations exhibiting an apparent decrease in life expectancy and others an apparent increase.[173]
Observational studies[edit]
Based on the subsistence patterns and biomarkers of foragers studied in the last century, advocates argue that modern humans are well adapted to the diet of their Paleolithic ancestor.[174] The diet of modern forager groups is believed to be representative of patterns for humans of fifty to twenty-five thousand years ago,[174] and individuals from these and other technologically primitive societies,[175][176] including those individuals who reach the age of 60 or beyond,[27][177] seem to be largely free of the signs and symptoms of chronic disease (such as obesity, high blood pressure, nonobstructive coronary atherosclerosis, and insulin resistance) that universally afflict the elderly in western societies (with the exception of osteoarthritis, which afflicts both populations).[2][4][174] Moreover, when these people adopt western diets, their health declines and they begin to exhibit signs and symptoms of "diseases of civilization".[3][174] In one clinical study, stroke and ischaemic heart disease appeared to be absent in a population living on the island of Kitava, in Papua New Guinea, where a subsistence lifestyle, uninfluenced by western dietary habits, was still maintained.[27][178]
One of the most frequent criticisms of the Paleolithic diet is that it is unlikely that preagricultural foragers suffered from the diseases of modern civilization simply because they did not live long enough to develop these illnesses, which are typically associated with old age.[4][7][179][180][181]According to S. Jay Olshansky and Bruce Carnes, "there is neither convincing evidence nor scientific logic to support the claim that adherence to a Paleolithic diet provides a longevity benefit."[181] In response to this argument, advocates of the paleodiet state that while Paleolithic foragers did have a short average life expectancy, modern human populations with lifestyles resembling that of our preagricultural ancestors have little or no diseases of affluence, despite sufficient numbers of elderly.[4][182] In forager societies where demographic data is available, the elderly are present, but they tend to have high mortality rates and rarely survive past the age of 80, with causes of death (when known) ranging from injuries to measles and tuberculosis.[183]
Critics further contend that food energy excess, rather than the consumption of specific novel foods, such as grains and dairy products, underlies the diseases of affluence.[7][71][184] According to Geoffrey Cannon,[7] science and health policy advisor to the World Cancer Research Fund, humans are designed to work hard physically to produce food for subsistence and to survive periods of acute food shortage, and are not adapted to a diet rich in energy-dense foods.[185] Similarly, William R. Leonard, a professor of anthropology at Northwestern University, states that the health problems facing industrial societies stem not from deviations from a specific ancestral diet but from an imbalance between calories consumed and calories burned, a state of energy excess uncharacteristic of ancestral lifestyles.[184]
Intervention studies[edit]
The first animal experiment on a Paleolithic diet suggested that this diet, as compared with a cereal-based diet, conferred higher insulin sensitivity, lower C-reactive protein and lower blood pressure in 24 domestic pigs.[186] There was no difference in basal serum glucose.[186] The first human clinical randomized controlled trial involved 29 people with glucose intolerance and ischemic heart disease, and it found that those on a Paleolithic diet had a greater improvement in glucose tolerance compared to those on a Mediterranean diet.[5][187] Furthermore, the Paleolithic diet was found to be more satiating per calorie compared to the Mediterranean diet.[188]
A clinical, randomized, controlled cross-over study in the primary care setting compared the Paleolithic diet with a commonly prescribed diet for type 2 diabetes. The Paleolithic diet resulted in lower mean values of HbA1c, triacylglycerol, diastolic blood pressure, body mass index, waist circumference and higher values of high density lipoprotein when compared to the Diabetes diet. Also, glycemic control and other cardiovascular factors were improved in both diets without significant differences. It is also important to note that the Paleolithic diet was lower in total energy, energy density, carbohydrate, dietary glycemic load and glycemic index, saturated fatty acids and calcium, but higher in unsaturated fatty acids, dietary cholesterol and some vitamins.[189] Two clinical trials designed to test various physiological effects of the Paleolithic diet are currently underway,[190][191] and the results of one completed trial[192] have shown metabolic and physiologic improvements.[6] The European Journal of Clinical Nutrition published a study[193] of a trial of the Paleolithic diet in 20 healthy volunteers. The study had no control group, and only 14 individuals completed the diet. In the study, in three weeks there was an average weight reduction of 2.3 kg, an average reduction in waist circumference of 1.5 cm (about one-half inch), an average reduction in systolic blood pressure of 3 mm Hg, and a 72% reduction in plasminogen activator inhibitor-1 (which might translate into a reduced risk of heart attack and stroke.) However, the NHS Knowledge Service pointed out that this study, like most human diet studies, relied on observational data. The NHS concluded that the lack of a control group, and the small sample of size of the study, compromises their conclusions. With only 14 participants the study lacks the statistical power to detect health improvements, and perhaps the simple fact that these 14 individuals knew that they were on a diet program made them more aware of weight and exercise regime, skewing the results.[194]
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Reception[edit]
Critics have argued that to the extent that foraging societies fail to suffer from "diseases of civilization", this may be due to reduced calories in their diet, shorter average lifespans, or a variety of other factors, rather than dietary composition.[141] Some researchers have also taken issue with the accuracy of the diet's underlying evolutionary logic or suggested that the diet could potentially pose health risks.[71][72][140][141]
A 2011 ranking by U.S. News & World Report, involving a panel of 22 experts, ranked the Paleo diet lowest of the 20 diets evaluated based on factors including health, weight-loss and ease of following.[195] These results were repeated in the 2012 survey, in which the diet tied with the Dukan diet for the lowest ranking out of 29 diets; U.S. News stated that their experts "took issue with the diet on every measure".[195] In the 2013 rankings, the Paleo diet tied for last place out of 29, and in 2014, it tied for last out of 32. However, one expert involved in the ranking stated that a "true Paleo diet might be a great option: very lean, pure meats, lots of wild plants. The modern approximations… are far from it."[195] He added that "duplicating such a regimen in modern times would be difficult."[195]
The U.S. News ranking assumed a low-carb version of the paleo diet, specifically containing only 23% carbohydrates.[196] Higher carbohydrate versions of the paleo diet, which allow for significant consumption of root vegetables,[197] were not a part of this ranking.[195] Dr. Loren Cordain, a proponent of a low-carbohydrate Paleolithic diet, responded to the U.S. News ranking, stating that their "conclusions are erroneous and misleading" and pointing out that "five studies, four since 2007, have experimentally tested contemporary versions of ancestral human diets and have found them to be superior to Mediterranean diets, diabetic diets and typical western diets in regard to weight loss, cardiovascular disease risk factors and risk factors for type 2 diabetes."[63][64][198] The editors of the U.S. News ranking replied that they had reviewed the five studies and found them to be "small and short, making strong conclusions difficult".[64]