High Glycemic Foods: Affects on Obesity & Disease
Are high glycemic diets a cause of obesity and disease in America today? Obesity and chronic diseases such as diabetes and cardiovascular disease are at an all time high in the United States; studies link a high glycemic diet with obesity and chronic disease. The Worldwide Health Organization (WHO) reports that there are more than 1 billion overweight adults globally” (WHO, 2010). According to a 2005-2006 CDC study of the United States population, 34% of adults are obese. In addition, the International Diabetes Federation announced in 2006 that diabetes is becoming the epidemic of the 21st century with 246 million people affected worldwide (Lefebvre, 2006). Diabetes currently affects 23.5 million adults and 2 million adolescents in the United States with 1.6 million new cases diagnosed each year (American Diabetes Association, 2007). The WHO also reports that heart disease is the top cause of death in the world and in high-income countries like the United States (WHO, 2004). In 2006 the American Heart Association estimated that 81,100,000 million people in the United States have some form of Heart Disease (American Heart Association, 2006). Despite the fact that high glycemic foods do not affect all people the same way, high glycemic diets are killing Americans because they increase the risk of obesity and disease.
High glycemic diets are prevalent in America today. Due to the rise of coronary heart disease in the 1970’s and 1980’s, the USDA came out with a new food pyramid in 1992 (Willett & Stampfer, 2002). Other countries with virtual no heart disease who ate low fat, high carbohydrate (but high-fiber, low glycemic) diets were the model followed in developing this new food pyramid. The food pyramid was based on the assumption that carbohydrates are good and fats are bad. The response by the American food industry was to produce high glycemic carbohydrate products that contained little fat but also contained little to no fiber or nutritional value (Palfreman, 2004).
This low fat craze and the food pyramid that has supported it continue to have a tremendous affect on the amount of carbohydrates that Americans consume. “Because protein intake for most individuals remains within a fairly narrow range, reductions in dietary fat tend to cause a compensatory rise in carbohydrate consumption” (Ludwig, 2010). Since 1970, there has been a 50% rise in carbohydrate consumption in the United States (USDA, 2002). This dietary change was not only supported by the USDA but also the medical community and in the schools where the food pyramid was displayed and taught (Palfreman, 2004).
America eats high glycemic foods in the form of refined grains, sugar, processed carbohydrates, and fast food. According to the USDA consumers eat too much refined grain and not enough whole grain (USDA, 2002). Although we consume less food in the form of carbohydrates than those in the early 1900’s, the whole grain carbohydrates they ate have been replaced with the refined or processed carbohydrates of today (Liebman, 1999). Eighty percent of the carbohydrates consumed by children between the ages of two and eighteen are higher on the glycemic index than sugar (Ludwig, 2002). The USDA also reports that sugar consumption hit a record high in 1999 and is the number one food additive. The recommended daily allowance of sugar per day is about 10 teaspoons, but the average American has an intake of about 32 teaspoons (USDA, 2002). Processed foods are also at an all time high; they include foods that are boxed, canned, or labeled (Hyman, 2008). The processing of carbohydrates increases the glycemic index of the food and decreases its nutrients (Harvard School of Public Health, 2010). Americans spend about 90% of their food budget on processed foods (Chuang, 2009). Also, because many Americans are on the go, fast food consumption has become a normal part of the American culture. There has been a 1000% increase in the number of fast food chains since 1970 (The Healthy Eating Guide, 2010) and a 300% increase in fast food sales from 1970 to 1980 (Paeratakul, Ferdinand, Champagne, & Bray, 20003). The new American diet has become a health risk. What America needs to learn is that all calories, including carbohydrates are not created equally. “You eat not only calories but also information. Eat the wrong information and you give your genes instructions to make you fat. Eat the right information and you give your genes instructions to lose weight” (Hyman, 2008). The food we eat also gives “information” to our bodies that can cause disease. To understand this concept in regards to high glycemic carbohydrates, we first need to understand the basics of carbohydrates, the glycemic index, and glycemic load.
A carbohydrate is composed of sugars. Sugars are essential and are required for energy. Unused sugars are stored in the body as fat and can be drawn on for later energy use. Carbohydrates can be classified into simple and complex: simple carbohydrates contain one or two sugar molecules whereas complex carbohydrates contain a chain of simple sugars (Harvard School of Public Health, 2010). It used to be thought that the blood glucose response to a carbohydrate was based on the chain length of a carbohydrate. This has proved to be inaccurate; many complex carbohydrates have shown to cause an even higher glucose response than sugar. This discovery has led to a new way to classify carbohydrates (Ludwig, 2002).
The glycemic index has proven to be a better method of rating carbohydrates because it takes an actual measurement of the blood glucose response to a particular carbohydrate. Foods are rated on a scale; the higher the rating, the higher that food is on the glycemic index. A high glycemic index food will cause the blood glucose level to rise higher and more quickly than a low glycemic index food. A low glycemic index food has a more stabilizing affect on the blood glucose level. Quantity of a carbohydrate is also important because the more consumed, the more affect on blood glucose response. One example is a carrot; although it is high on the glycemic index, the number of carbohydrates in a carrot is so small that it has little effect on the blood glucose level. High glycemic load considers both the quality of the carbohydrate (high glycemic index) and the quantity of the carbohydrate (how many carbohydrates in a food item) (Higdon, 2005). A high glycemic diet is one that is based on foods that have a high glycemic load. A high glycemic diet might include foods such as white bread, white flour, sugar, potatoes, white pasta, white rice, and other highly processed or packaged foods (Harvard School of Public Health, 2010).
Now, back to how different carbohydrates send different “information” to the body. When a carbohydrate is consumed, the body starts breaking that food item into sugars. A low glycemic food takes longer to be broken down into sugars and thus provides a longer digestive cycle and a longer feeling of satiety. Because a high glycemic food is already broken down into its simplest form, whether through its simple nature or by human processing, the energy (or sugars) it gives comes all at once. The quick digestion of a high glycemic food causes the excess energy to be stored as fat. On the other hand, the rate of digestion for a low glycemic food allows the body to use the energy from that food over time where less gets stored as fat (Brand-Miller, et al., 2003). Therefore, a high glycemic meal when compared to a low glycemic meal with the same number of calories can cause more fat storage. One might think, “What is the difference? Won’t the body just use the energy stored as fat and continue to get the energy it needs?” The problem is that after a high glycemic meal, the blood glucose level rises quickly, and several hours later this leads to an unnatural low. The body, sensing that blood sugar is too low sends signals to your brain in the form of hunger and cravings. “There are many reasons for cravings. But the main one is that your blood sugar is swinging up and down, putting you on a seesaw of hunger and craving” (Hyman, 2008). Studies show that a high glycemic diet actually increases calorie intake.
In one study, 12 obese boys were given several different kinds of breakfasts: low glycemic, medium glycemic and high glycemic. Later that day, the boys were allowed to eat as much as they wanted in a buffet style lunch. When the boys had a medium glycemic breakfast, they ate 53% more at lunch than what they had a low glycemic breakfast and 81% more at lunch if they had a high glycemic breakfast (Ludwig, et al., 1999). Another similar study of 37 grade school children ages 9 to 12 ran a breakfast club where the type of breakfast was controlled. Again at lunch the children were allowed to eat buffet style. This study came to the same conclusion that children ate more at lunch after a high glycemic breakfast than after a low glycemic breakfast. This study further suggested that the weight of the child was not a factor in determining if the child ate a bigger lunch (Warren, Henry, & Simonite, 2003). The blood glucose affect of high glycemic foods seems to be the root cause of overeating. Another study of 16 adolescents tested hunger levels after low and high glycemic meals. Food was requested sooner after a high glycemic meal than after a low glycemic meal (Ball, et al., 2003). One study concluded that a 50% increase in the glycemic index of meal meant a 50% decrease in satiety (Brand-Miller, 2003). All of these studies determined that high glycemic meals promote hunger, excess eating, and could lead to obesity.
Other “information” that is sent to the body affects the body’s ability to burn fat as fuel. Fat oxidation or fat burning is the process used by the body to take stored fat and use it as energy. Ingested fats are broken down by the body and are chemically changed into fatty acids. Fatty acids are released by adipose (fat) tissue and absorbed by cells as energy. In order for the fatty acids to be released, hormone-stimulating lipase (HSL) must be activated. HSL is activated by another hormone called acetyl-CoA carboxylase (ACC) which regulates fat oxidation. Insulin (a hormone produced in large amounts after a high glycemic meal) inhibits the activation of ACC which in turn inhibits the activation of HSL and the release of energy from fat storage (King, 2009). Ludwig’ study on 12 obese boys found that high glycemic meals produced lower fatty acid concentrations and lower fat oxidation rates throughout the day than did the low glycemic meals (Ludwig, et al., 1999). In a study on the glycemic index and obesity Brand-Miller states, “Longer exposure to chronic hyperglycemia and hyperinsulinemia (high blood glucose and insulin levels) results in decreased expression of the rate-limiting enzymes and alters the potential for fat oxidation. Reduced rates of fat oxidation were linked with greater weight gain in several prospective studies” (Brand-Miller, 2003). Thus, a high glycemic diet not only affects satiety and calorie intake but stimulates the storage of fat.
A low glycemic diet has been shown to manage, reverse, and prevent obesity. Although obesity was thought to be caused from excessive fat intake, studies have not shown that eating high levels of fat causes weight gain. In fact, fat intake has decreased since the 1960’s while obesity has continued to rise. Obesity is not a problem of eating too much food but of eating the wrong food. Low fat diets in America have become equivalent to a high glycemic diet and there is much evidence to suggest that a low glycemic diet can prevent obesity. A low glycemic diet increases satiety, keeps blood glucose levels stable, and increases fat oxidation. Although more long term studies are needed, “a growing body of theoretical and experimental work suggests that diets designed to lower the insulin response to ingested carbohydrate (e.g., low GI) may improve access to stored metabolic fuels, decrease hunger, and promote weight loss” Ludwig, 2002).
Carbohydrates that “send your genes information to make you fat,” can also send “information” to give you chronic disease (Hyman, 2008). “Despite inconsistencies in the data, sufficient, positive findings have emerged to suggest that the dietary glycemic index is of potential importance in the treatment and prevention of chronic disease” (Willet, et al., 2002). While studies have conclusively linked chronic diseases such as diabetes and cardiovascular disease with a high glycemic diet, it may also have significance to cancer prevention. Insulin resistance correlates to certain “diet-related” cancers: colon, breast, and prostate. Preliminary studies show an association with colon cancer. Ovarian cancer may also be linked to a high glycemic diet. Insulin resistance is not only a risk factor for some cancers but for diabetes and cardiovascular disease as well (Jenkins, et al., 2002).
We have already established that high glycemic foods cause the blood glucose level to rise rapidly. Any rise in the blood glucose level will signal the pancreatic beta-cells to produce insulin; insulin is the hormone that instructs cells to store excess energy as fat for future use. A high glycemic meal puts excess demands on the pancreas because it requires excess amounts of insulin to be secreted. “High GI foods elicit, calorie for calorie, higher insulin levels… than low GI foods” (Ludwig, 2002). Over time the pancreas can wear down and the body can become resistant to the high levels of insulin being produced resulting in type 2 diabetes.
Several studies support dietary affects on the risk of type 2 diabetes. In a 2004 study that followed the eating patterns of 36,787 men and women without diabetes over a 4 year period it was concluded that those with a high dietary intake of white bread and starch had an increased risk of type 2 diabetes (Hodge, English, O’Dea, & Giles, 2004). Another study that examined the association between consumption of sugar-sweetened beverages, weight change, and the risk of type 2 diabetes in women over an 8 year period found that women consuming one or more sweetened soft drinks a day had a higher risk of type 2 diabetes than women who drank one a month (Schulze, et al., 2004). Also, a study of nurses and men in the medical field showed that those who consumed white bread and potatoes were associated with a higher risk of type 2 diabetes (Willett, Manson, & Liu, 2002).
Cardiovascular disease is also connected with a high glycemic diet. There is an association with several predictors of cardiovascular disease and a high glycemic diet: increase triglyceride concentrations and low-density lipoprotein (LDL), decreased high-density lipoprotein (HDL), and increased serum levels of C-reactive protein (Liu, et al., 2000). LDL and HDL cholesterol are fatty substances that build cell membranes and produce essential hormones. LDL is sent out to the body through the bloodstream and can build up on artery walls causing atherosclerosis. HDL extracts cholesterol from artery walls and brings them back to the liver. An imbalance of HDL and LDL is called hyperlipidimia (Medterms.com). Hyperlipidemia, or high cholesterol, is a condition of raised or abnormal lipids (fats) in the blood. These lipid abnormalities are a risk factor in cardiovascular disease. A high glycemic diet increases this risk because the high production of insulin causes the liver to produce cholesterol rather than use the cholesterol that is already in the bloodstream (Lee & Kulick, 2009). C-reactive protein (CRP) levels increase when arteries are inflamed; this indicates artery narrowing. This condition results from plaque buildup on the artery walls which can be caused from high insulin levels (American Heart Association, 2010). Triglycerides are made up of fatty acids and provide energy to the cells. Although there is not a clear association between triglycerides and cardiovascular disease, several recent studies have shown an increase risk with elevated triglyceride levels (Lee, et al., 2009).
Other factors that increase the risk of cardiovascular disease is the hyperglycemia (low blood glucose) and hypoglycemia (high blood glucose) associated with a high glycemic diet. These ups and downs of the blood glucose level can lead to high blood pressure, high cholesterol, and blood clotting; all of which are cardiovascular risks. “The current low-fat, high-carbohydrate diet recommended in the United States may not be optimal for the prevention of CHD and could actually increase the risk in individuals with high degrees of insulin resistance and glucose intolerance” (Liu, Willett, Stampfer, Hu, & Franz, 2000).
Studies support this correlation between a high glycemic diet and cardiovascular disease. A ten year follow up study of over 700,000 people suggested a high glycemic diet increased the risk of coronary heart disease (Liu, et al., 2000). A study of Japanese women whose staple included high glycemic white rice concluded that there is a positive association between a high glycemic diet and risk of cardiovascular disease (Amano, Kakubo, Lee, Tang, Sugiyama, & Mori, 2004).
Just as a high glycemic diet increases the risk of chronic disease, a low glycemic diet may reduce the risk of both diabetes and cardiovascular disease by decreasing risk factors of these diseases. “Researchers estimate that 90% of type 2 diabetes cases could be prevented through a combination of a healthy diet and an active lifestyle” (Harvard School of Public Health). Since the main goal in diabetes management is to stabilize the blood glucose level and the slow digestion of low glycemic foods help in that stabilization, it makes a lot of sense that a low glycemic diet is a good way to manage, prevent, or even possibly reverse diabetes. Eight out of nine studies determined that glycemic control was increased with a low glycemic diet in both type 1 and type 2 diabetic subjects. Low glycemic diets have been proven to lower urinary C-peptide excretion which indicates less insulin production (Willett, Manson, & Liu., 2002). Low glycemic diets have also shown to increase insulin sensitivity and to reverse high cholesterol. This is because a low glycemic diet helps stabilize blood glucose levels and decrease hypoglycemic events. This means that less fatty acids and regulatory hormones are produced (Leeds, 2002). Low glycemic diets are also associated with higher HDL concentrations, lower LDL concentrations, and lower triglyceride levels (Jenkins, et al., 2002). Willett suggests that simple dietary changes such as replacing white flour and potatoes with whole grains will reduce the risk of cardiovascular disease (Willett, et al., 2002). America is a world leader in obesity and chronic disease. America is the first country to ever adopt a low fat, high glycemic diet and the affects have been staggering (Palfreman, 2008). Research confirms that the high glycemic diet of America correlates directly to obesity and disease in this country: insulin resistance, high cholesterol, decreased fat oxidation, and low satiety. Unless we reverse the trend from high glycemic to low glycemic food consumption, Americans will continue to die senselessly from preventable diseases.

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