According to a United Health Foundation study, obesity has increased by 110 percent since 1990, and while it seems Americans are on a weight-loss binge - counting carbs, participating in fad diets and avoiding fat like it is some type of poison - nearly one-quarter of Americans are now considered obese. However, according to some nutritionists, it is not the carbs and fat that are the problem. Instead, they say the real source of the problem is one often-overlooked ingredient that has saturated our food and beverages - high fructose corn syrup.
High fructose corn syrup is used in everything from soda to cereal. It lurks in processed applesauces, jellies, ice creams, salad dressings and even bread. It is close to becoming the most consumed sweetener in the United States, just barely lagging behind sugar.
The process for producing the sweetener out of corn was developed in the 1970s. Consumption of the ingredient increased dramatically in the 1980s, according to USDA reports. It was around this time that obesity rates in the United States began steadily rising.
This fact has many questioning whether the 1,090 percent increase in high fructose corn syrup processed for individual food and beverage consumption - from 4.9 pounds per person a year in 1975 to 58.3 pounds per person a year in 2006 - is a cause of the rising obesity rates.
The answer is not simple. Are Americans simply exercising less and consuming oversized portions? Are Americans consuming more empty calories as a result of high fructose corn syrup showing up in an ever-increasing number of products, or does the specific metabolism of fructose in our bodies facilitate weight gain?
According to a study by Dr. Peter J. Havel, D.V.M. and associate researcher in the nutrition department at the University of California-Davis, the way the body metabolizes fructose differs from how glucose is metabolized. Whereas glucose can be metabolized by cells as well as in the liver, the majority of fructose must be metabolized in the liver.
Once in the liver, said Havel, fructose and glucose follow different enzyme pathways. As a result, fructose metabolism favors lipogenesis, the production of lipids, or fat.
With a high fructose diet, there is a possibility that it could contribute to an accumulation of fat in the liver,"" Havel said. ""Fat in the liver is associated with cardio disease and diabetes.""
The study also state that fructose does not stimulate insulin or leptin production. Both of these hormones contribute to a feeling of satiety and a decrease in appetite. Another hormone - ghrelin - stimulates appetite. While glucose acts to decrease this hormone, consumption of fructose does not.
While these factors all support the idea that fructose contributes to weight gain more than glucose, Havel stressed that further studies need to be done and that the chemical composition of high fructose corn syrup is not all that different from table sugar.
""Basically, sucrose [table sugar], composed of 50 percent fructose and 50 percent glucose, and high fructose corn syrup, usually 55 percent fructose and 45 percent glucose, are quite similar in their composition,"" said Havel. ""It is the fructose that they [both] contain and the quantity consumed that may lead to undesirable health outcomes.""
Dr. Marion Nestle, M.P.H. and professor of nutrition, food studies and public health at New York University agreed. She said the problem with high fructose corn syrup does not have anything to do with how the body metabolizes it but with how much of it individuals consume.
""I'm not convinced the body can tell the difference [between high fructose corn syrup and table sugar],"" said Nestle.
Despite this, Nestle believes the dramatic increase in consumption of high fructose corn syrup in the past 30 years has significant health implications.
""High fructose corn syrup is cheaper [than table sugar], which is an encouragement to use more of it."" said Nestle. ""It's cheap empty calories.""
Shannon McNamara, representative for the Corn Refiners Association, spoke up against claims that high fructose corn syrup contributed to the rise in obesity.
""No single food or ingredient is the sole cause of obesity,"" she said, ""but rather too many calories and too little exercise is the primary cause. High fructose corn syrup is not higher in calories than any other nutritive sweetener. Both sugar and high fructose corn syrup contain four calories per gram.""
McNamara said the scientific information circulating that relates pure fructose to weight gain is incorrectly associated with high fructose corn syrup because high fructose corn syrup contains both fructose and glucose, not fructose alone.
The results of Havel's study confirm this.
When some participants were fed meals containing high fructose corn syrup and other meals containing table sugar, there were no substantially different effects on insulin, leptin and ghrelin hormone production. The level of circulating triglycerides, a risk factor for cardiovascular diseases, rose in individuals after both high fructose corn syrup and table sugar consumption.
What may be important is to realize one's own health needs and monitor one's consumption of sweeteners - regardless of the source.
""If you are a young, healthy, active individual, one soda a day is unlikely to have much of an impact on weight and health,"" said Havel. ""On the other hand, if you are overweight or obese and at risk for cardio diseases or diabetes, you should avoid high sugar intakes.""
With the overall consumption of sugars - including both high fructose corn syrup and table sugar - increasing 19 percent from 1992 to 2006, perhaps dieters and health-enthusiasts should ease up on the carb-counting and the fat-free fixation, and focus more attention on a sweet little additive that may contain a surprisingly sour bite.
