Study: High-fructose corn syrup causes more weight gain

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Water sweetened with high-fructose corn syrup. Image courtesy: Princeton University, Office of Communications, Denise Applewhite

Rats given high-fructose corn syrup were more likely to put on excess weight compared with those who ate sucrose (common table sugar), even when both groups consumed the same total number of calories, according to findings from a new study from researchers at Princeton University. The study, published online in the journal Pharmacology, Biochemistry and Behavior, found that, not only did rats consuming high-fructose corn syrup gain more weight than those eating sugar, but they also had abnormal increases in body fat, particularly in the abdomen and in the form of elevated triglyceride levels in the blood. According to Bart Hoebel, a professor of psychology and author of the new study, the findings dispute claims that high-fructose corn syrup is little different from other sweeteners when it comes to adverse health effects.

In an initial experiment, Hoebel and colleagues from the Princeton Neuroscience Institute gave male rats water sweetened with either high-fructose corn syrup or sucrose (standard table sugar) in addition to their standard diet of rat feed. The concentration of sugar was roughly the same as that found in commercial sodas, while the concentration of high-fructose corn syrup was half that found in soda. Despite the difference in sweetener concentration, rats in the high-fructose corn syrup group gained significantly more weight.

In a second experiment, researchers tracked weight gain, body fat and triglycerides in rats eating only rat feed, compared with those regularly consuming high-fructose corn syrup. Researchers found that, compared with those on a standard rat diet, those eating the high-fructose corn syrup gained significantly more weight, and had higher concentrations of body fat and triglycerides, symptoms in keeping with what is known as metabolic syndrome in humans. Male rats in particular put on a significant amount of excess weight during the six-month study, gaining 48% more weight than those on the standard diet.

Understanding the mechanisms that drive the different weight gain and fat composition among rats consuming the different sweeteners is an important next step in the research, but Hoebel and colleagues speculate that the chemical composition of high-fructose corn syrup likely plays a significant role. Whereas sucrose (table sugar) is roughly half glucose and half fructose, two simple sugar molecules, the corn-based sweetener has a higher ratio of fructose to glucose, in addition to a small level of more complex sugars known as saccharides. Also, during the manufacture of high-fructose corn syrup, the different sugar molecules are broken apart, making them easier to process immediately in the body. In contrast, sucrose requires an additional metabolic step to process in the body.

Though high-fructose corn syrup was first introduced into food manufacturing in 1970, its impact on the body is still being understood. Despite a recent series of TV ads promoting high-fructose corn syrup as little different from other sweeteners and “fine in moderation,” a recent study from Duke University Medical Center suggests that, for some patients at least, it could have a harmful impact. In the study of patients with non-alcoholic fatty liver disease (NAFLD), researchers found that those who consumed higher levels of high-fructose corn syrup had greater incidence of liver scarring.

At the very least, this latest study from Princeton suggests that additional research into the popular sweetener is necessary, and Hoebel and colleagues already have plans to investigate how the combination of a high-fat diet together with high-fructose corn syrup consumption impacts weight gain or potentially contributes to disease associated with obesity. Yet, in the meantime, while research is ongoing, Hoebel suggests that these latest findings contribute to the theory that high-fructose corn syrup may be a significant contributing factor to the obesity epidemic.