A class of hormones known as POMC peptides, which regulate body weight, acts differently in female mice than in male mice, according to a collaboration of researchers across four continents. The difference appears to make it harder for female mice to lose weight.

POMC peptides are produced in the brain and play a role in appetite, calorie burning and physical activity, all of which impact overall body weight. When genetically engineered obese mice were given the weight-reducing medication lorcaserin, the males experienced significant weight loss, pushing them back into the healthy range, whereas the female mice saw much smaller weight losses and remained obese.

"(W)hat we have discovered is that the part of the brain that has a significant influence on how we use the calories that we eat is wired differently in males and females," team leader Lora Heisler, of the University of Aberdeen, in Scotland, said in a press release.

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In the female mice, the source of POMC peptides reduces appetite, but it does not raise physical activity or calorie burning the way it does in male mice.

Two of every three adults and one in three children and adolescents in the United States are overweight or obese, according to the National Institutes of Health.

"These findings provide evidence that males and females are hard-wired differently in their regulation of energy balance," the study's authors wrote in the journal Molecular Metabolism. "Given the reported reduction of POMC neuron activity in middle age in mice, these data may have ... broad implications for future sex-specific strategies in treating overweight [problems] and obesity."