Mood hormone may affect fat, U.S. study finds

By Maggie Fox, Health and Science Editor

WASHINGTON (Reuters) - A brain chemical strongly linked to mood and appetite may also directly affect fat gain, U.S. researchers reported on Tuesday.

They said levels of serotonin, the nerve-signaling chemical targeted by many antidepressants, may also direct the body to put down fat regardless of how much food is eaten.

"It may be one reason diets fail," metabolism expert Kaveh Ashrafi of the University of California, San Francisco, who led the study, said in a telephone interview.

The findings, published in the journal Cell Metabolism, could lead to better diet drugs and treatments for diseases like diabetes.

Serotonin may help the body decide whether to burn off excess calories, or store them as fat, Ashrafi said.

He worked with roundworms for his experiment but said the findings may relate to humans. "These worms, although they are microscopic, they have around 20,000 genes ... and if you compare them side by side they are about 50 percent similar to us," he said.

Genes controlling appetite, fat storage and metabolism are especially similar, he said. The tiny worms can be manipulated to see changes to their metabolism, appetite and weight gain.

"It has been known for a long time that increasing serotonin causes fat reduction," Ashrafi said.