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Common Sweetener Linked to Obesity

Fructose induces leptin resistance and may lead to obesity

MONDAY, Oct. 20 (HealthDay News) -- Leptin resistance may develop silently as a result of high fructose consumption and worsens weight gain in response to a subsequent high-fat diet, according to a report released online in advance of publication in an upcoming issue of the American Journal of Physiology - Regulatory, Integrative and Comparative Physiology.

Alexandra Shapiro, Ph.D., of the University of Florida in Gainesville, and colleagues examined the effect of a high-fructose diet on leptin resistance. Sprague-Dawley rats were fed either a 60 percent fructose or fructose-free control diet for six months with assessment of leptin resistance. Half of the rats were then switched to a high-fat diet and intraperitoneal leptin injections were given.

While chronic fructose consumption was associated with leptin resistance, no differences in serum leptin levels, weight or adiposity were noted with the control rats that remained leptin responsive, the investigators found. Food intake significantly declined following intraperitoneal leptin injections in rats with a fructose-free diet, but had no effect in fructose-fed rats. Following the incorporation of a high-fat diet, leptin-resistant rats had an exaggerated weight gain (about 50.2 g) compared to leptin-responsive rats on the same high-fat diet (about 30.4 g), the researchers report.

"A key finding in this study is that a silent leptin resistance has occurred with almost no physiological or biochemical differences detected between the fructose- and control-fed groups," the authors conclude. "Thus, high-fructose diet predisposes to obesity, and deleterious effects of chronic fructose consumption develop long before any visible signs of elevated leptin or the metabolic syndrome. The significance is that this mechanism might well explain why fructose ingestion is associated with obesity."

One of the co-authors of the study holds several patent applications related to fructose and obesity, and has a lay book on fructose that was published by Rodale, Inc. in 2008.

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