More Evidence For Fructose Obesity Link

Fructose fruit sugar is not a harmless substitute for glucose.

University of Florida researchers have identified one possible reason for rising obesity rates, and it all starts with fructose, found in fruit, honey, table sugar and other sweeteners, and in many processed foods.

Fructose may trick you into thinking you are hungrier than you should be, say the scientists, whose studies in animals have revealed its role in a biochemical chain reaction that triggers weight gain and other features of metabolic syndrome - the main precursor to type 2 diabetes. In related research, they also prevented rats from packing on the pounds by interrupting the way their bodies processed this simple sugar, even when the animals continued to consume it.

The findings, reported in the December issue of Nature Clinical Practice Nephrology and in this month's online edition of the American Journal of Physiology-Renal Physiology, add to growing evidence implicating fructose in the obesity epidemic and could influence future dietary guidelines. UF researchers are now studying whether the same mechanism is involved in people.

"There may be more than just the common concept that the reason a person gets fat is because they eat too many calories and they don't do enough exercise," said Richard J. Johnson, M.D., the J. Robert Cade professor of nephrology and chief of nephrology, hypertension and transplantation at UF's College of Medicine. "And although genetic predispositions are obviously important, there's some major environmental force driving this process. Our data suggest certain foods and, in particular, fructose, may actually speed the process for a person to become obese."

Physical inactivity, increased caloric intake and consumption of high-fat foods undoubtedly account for part of the problem, Johnson said. But Americans are feasting on more fructose than ever. It's in soft drinks, jellies, pastries, ketchup and table sugar, among other foods, and is the key component in high fructose corn syrup, a sugar substitute introduced in the early 1970s.

Since then, fructose intake has soared more than 30 percent, and the number of people with metabolic syndrome has more than doubled worldwide, to more than 55 million in the United States alone, Johnson said. The condition, characterized by insulin resistance, obesity and elevated triglyceride levels in the blood, is linked to the development of type 2 diabetes and hypertension.

"If you feed fructose to animals they rapidly become obese, with all features of the metabolic syndrome, so there is this strong causal link," Johnson said, "And a high-fructose intake has been shown to induce certain features of the metabolic syndrome pretty rapidly in people."