Weight Loss Linked to Low Levels of Fat Hormone

Also associated with changes in brain activity that involve eating behavior

MONDAY, June 23 (HealthDay News) -- Weight loss in obese individuals is associated with changes in brain activity in areas associated with eating behavior that can be reversed by injections of leptin, a hormone secreted by fat cells whose levels appear to fall with weight loss, according to a report published online June 20 in the Journal of Clinical Investigation.

Michael Rosenbaum, M.D., and colleagues from Columbia University Medical Center in New York City, examined neural activity by functional MRI in response to food-related visual cues in six obese individuals before and after a 10 percent weight loss. After weight loss, subjects were injected twice a day with leptin or placebo.

The researchers found that after weight loss, there were changes in the activity of brain areas involved in the regulatory, emotional and cognitive control of food consumption. There were increases in neural activity in the brainstem, culmen, parahippocampal gyrus, inferior and middle frontal gyri, middle temporal gyrus and lingual gyrus, and decreases in the hypothalamus, cingulate gyrus and middle frontal gyrus, all of which were reversible by leptin.

"Thus, leptin is a critical factor linking reduced energy stores to eating behavior," Rexford S. Ahima, M.D. Ph.D., from the University of Pennsylvania School of Medicine in Philadelphia, writes in an accompanying editorial. "Potentially, leptin therapy could sustain weight loss by overriding the tendency toward energy conservation."

Leptin for the study was provided by Amylin Pharmaceuticals Inc., and the author of the editorial disclosed financial ties to pharmaceutical companies.

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