Estrogen regulates appetite and body weight, while insufficient estrogen receptors in specific parts of the brain may lead to obesity, a new study finds.

"Estrogen has a profound effect on metabolism," said Dr. Deborah Clegg, an associate professor at the University of Texas and senior author of the study published in Cell Metabolism. "We hadn't previously thought of sex hormones as being critical regulators of food intake and body weight."

Estrogen working through two hypothalamic neural centers in the brain keeps the body weight of female mice in check by regulation of hunger and energy use in form of calories.

Female mice lacking estrogen receptor alpha (ER-α) a molecule that sends signals to neurons, specifically in the hypothalamic neural part of the brain, become obese and develop obese related disease such as diabetes and heart disease. Male mice did not have similar results.

Estrogen receptors are located throughout the body, but researchers found two specific estrogen receptors that appear to regulate energy balance for female mice.

Currently, long-term estrogen hormonal replacement therapies were stopped after 2002 study showed increased risk for cardiovascular disease.

The new results could lead to targeted hormonal replacement therapies for millions of post-menopausal women. The new target method would deliver estrogen to specific parts of the brain that regulate body weight, avoiding the risk of cardiovascular disease associated with full-body estrogen delivery.

“The role of estrogen in postmenopausal women continues to remain uncertain,” Clegg said.

"Current research is focused on the timing and the type of estrogen supplementation that would be most beneficial to women. Our findings further support a role for estrogens in regulating body weight and energy expenditure, suggesting a benefit of estrogen supplementation in postmenopausal women, she said."