A new study has identified the role of sex hormone estrogen in burgeoning waistlines in older women.
Researchers have traced hormonal effects on metabolism to different parts of the brain.
The findings may lead to the development of highly selective hormone replacement therapies that could be used to combat obesity or infertility in women without the risks for heart disease and breast cancer, the researchers say.
"When women approach menopause, they gain weight in fat and their energy expenditure goes down," said Deborah Clegg of the University of Texas Southwestern Medical Center.
Estrogen levels decline and women grow increasingly susceptible to obesity and metabolic syndrome.
Estrogen acts on receptors found throughout the body, in fat, on ovaries and in muscle. But when it comes to the hormone's influence on metabolism, Clegg suspected receptors in the brain.
Others had traced the effects of estrogen on energy balance specifically to estrogen receptor-a (ERa). When her team deleted those receptors from the entire brains of mice, "we got very, very fat mice," Clegg said. The animals consumed more calories and burned less.
The study has been published in the journal Cell Metabolism.