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An animal study suggests that consuming fructose—a simple sugar found in foods and in products like high-fructose corn syrup—may contribute to weight gain and other unhealthy metabolic changes, even in the absence of excessive caloric intake. Published in Scientific Reports, the study involved feeding two groups of mice a diet that was either 18% fructose—similar to the amount of fructose consumed by the top percentile of adolescents in the US—or 18% glucose (another simple sugar). Researchers also made sure that the calories in the diets of both groups of mice were the same. After observing the mice for 77 days, here is what the researchers discovered:

• Mice who consumed the fructose diet had significantly increased body weight, body fat, and liver fat, and a significant reduction in physical activity, when compared to the mice that consumed the glucose diet.
• It appears that the reduction in physical activity in the fructose-consuming mice might account for the weight gain that those mice experienced.
• No differences between the two groups were observed in cognitive or motor performance.

The study is of potential importance because it indicates that the negative effects associated with fructose consumption may come from the fructose itself, rather than from an accompanying increase in total caloric intake (since mice in both groups consumed a similar number of calories). Previous research on fructose had not clearly determined whether the negative metabolic changes were due to the fructose itself or simply to consuming more calories. It is important to note, however, that due to the relatively small amount of fructose present in fruits and vegetables, it is unlikely that the fructose in these foods would have any negative effects.

Source: Scientific Reports