Over the last 30 years there has been a dramatic increase in the incidence of overweight and obesity around the world. There have been many hypotheses as to why this is occurring including increasing portion sizes, decreasing activity, and increases in foods eaten away from home. In the United States this increase in obesity also has paralleled a shift away from the use of sucrose (table sugar) toward the use of High Fructose Corn Syrup (HFCS). This association led to a hypothesis that an increase in fructose intake from HFCS is a causative factor for obesity. Various misunderstandings and correlations have supported this hypothesis, including the following:

• Misunderstandings: HFCS is substantially higher in fructose content than sucrose; HFCS bypasses physiological processes that regulate satiety
• Correlations: Soft drinks are sweetened with HFCS; Soft drink consumption has increased
• Controversy: Soft drinks consumption is associated with poor calorie compensation that leads to excess calorie intake and weight gain

What the Science Supports

Two recent reviews help to clarify the misunderstandings about HFCS and its role in the etiology of obesity. One review occurred at a symposium titled “High Fructose Corn Syrup (HFCS): Everything You Wanted to Know, but Were Afraid to Ask” that was held at the Experimental Biology annual conference on April 30, 2007 in Washington, DC. A second review, conducted by a group of 10 experts assembled by the University of Maryland Center for Food, Nutrition, and Agriculture Policy (CFNAP), was published in the August 2007 issue of Critical Reviews in Food Science and Nutrition, titled “A Critical Examination of the Evidence Relating High Fructose Corn Syrup and Weight Gain.” Both reviews conclude that HFCS and sucrose are chemically similar and both are metabolized similarly by the body.

To put the issue into context, HFCS is high in fructose only compared to regular corn syrups, which do not contain fructose (only glucose). The most commonly used types of HFCS contain both glucose and fructose and thus are similar to sucrose and honey in their fructose and glucose content. As the supply of HFCS increased in the US since the 1970s, the supply of sucrose decreased—with the supply of sucrose today still exceeding that of HFCS, although marginally. And while the combined supply of sucrose and HFCS has increased over time, so has the per capita availability of total calories due to relatively larger increases in the availability of fats and oils and grain products. Thus neither the ratio of fructose to glucose from caloric sweeteners in the overall food supply nor the percentage contribution of caloric sweeteners to the per capita availability of calories has changed over the past several decades. In fact, the supply of total caloric sweeteners and HFCS has actually decreased slightly since 1999, while the rates of overweight and obesity are still increasing.

Studies in humans have shown decreased release of the satiety hormones insulin and leptin and increased release of the hunger hormone ghrelin when high doses of pure fructose (not HFCS) are administered when compared to glucose. However, human studies that compare HFCS and sucrose have shown no differences in these satiety hormones or in any other endocrine or metabolic responses. In fact, HFCS and sucrose lead to the same physiological responses when tested in normal weight or obese subjects, and in men and women. Importantly, these studies used beverages that supplied 25 to 30 percent of calories in the sweeteners, well exceeding the average 15 to 17 percent of calories provided by caloric sweeteners from all foods and beverages.

Some evidence exists that suggests that calories provided in liquid forms may provide less satiety than calories provided in solid forms, but other evidence contradicts this idea. As with most things in life, satiety is complex and influenced by factors such as the calorie content, volume or amount, and energy density (i.e., calories per serving size) of the item, and usage (for example, is it consumed separately prior to a meal or as part of a snack or meal). All beverages help meet hydration needs and when consumed with snacks and meals satisfy thirst and function as a lubricant to facilitate chewing and swallowing, which can affect the amount of either food or beverage consumed. Research has shown that all caloric beverages—regular soft drinks, fruit juice, and low fat milk—similarly affect total calorie intake when consumed with a meal and lead to similar caloric compensations.

As for evidence published in the peer-reviewed literature that directly links HFCS to overweight or obesity, very little exists and what does exist is inconclusive. Studies that describe associations between the availability of HFCS in the US food supply and prevalence of overweight and obesity do not prove cause and effect. Results from cross-sectional and longitudinal epidemiologic studies and randomized clinical trials of soft drink intake (a proxy for HFCS) and weight status are mixed. Furthermore, overweight and obesity worldwide are increasing even though HFCS is rarely used outside the US.

What can be said about HFCS? Dr. Peter Havel, from the University of California at Davis, summarized the Experimental Biology symposium well, stating, “We can all agree there are no large differences in the metabolic effects of HFCS and sucrose.” Dr. Richard Forshee, lead author of the CFNAP review, said the expert group concluded that HFCS does not appear to contribute to overweight and obesity any differently than does any other energy source with similar calories. As such, individuals need to be aware of how beverages contribute to calorie intake whether sweetened with HFCS or sucrose.