Washington, Oct 17 (IANS) Excess of fructose or fruit sugar in one’s diet can induce leptin resistance, a condition that can easily lead to obesity when combined with a high-fat, high-calorie diet, according to a new study on rats.Leptin is a hormone that plays a role in helping the body balance food intake with energy expenditure. When leptin isn’t working — that is, when the body no longer responds to the leptin it produces — it’s called leptin resistance.

Although previous studies have shown that being leptin resistant can lead to rapid weight gain on a high-fat, high-calorie diet, this is the first study to link it with high fructose consumption.

The study also showed for the first time that leptin resistance can develop silently, with little indication that it is happening.

The study was carried out by Alexandra Shapiro, Wei Mu, Carlos Roncal, Kit-Yan Cheng, Richard J. Johnson and Philip J. Scarpace, all from University of Florida College of Medicine in Gainesville.

Obesity is a growing problem worldwide and fructose has been suspected of playing a role. Fructose is the sugar found in fruit, but it’s not the normal consumption of fruit that is the problem.

Table sugar and high-fructose corn syrup are about 50 percent fructose and these ingredients have become increasingly common in many foods and beverages. With sugar and high-fructose corn syrup being added to many foods, people now eat much more fructose than ever before.

Florida researchers hypothesised that a high-fructose diet could lead to leptin resistance, which in turn could lead to exacerbated weight gain in the face of a high-fat, high-calorie diet, a typical diet in industrialised countries, said a release of University of Florida.

To test their hypothesis, the research team performed a study with two groups of rats. They fed both groups the same diet, with one important exception: one group consumed a lot of fructose while the other received no fructose.

During these six months, there were no differences in food intake, body weight, and body fat between rats on the high-fructose and the rats on the fructose-free diets.

Besides, there was no difference between the two groups in the levels of leptin, glucose, cholesterol or insulin found in their blood. There was only one difference at the end of the six months: The rats on the high-fructose diet had higher levels of triglycerides in their blood.

The first six months of the study showed that leptin resistance can develop silently. “Usually, leptin resistance is associated with obesity, but in this case, leptin resistance developed without obesity,” Shapiro said. “This was very surprising.”

Animals exposed to the high-fructose diet, the leptin resistant rats, ate more and gained much more weight and fat than the leptin responsive animals on the fructose-free diet.

The study appeared in the American Journal of Physiology.