The findings are potentially important for millions of postmenopausal women, many of whom have decided against hormonal replacement therapy (HRT).
"Estrogen has a profound effect on metabolism," said Deborah Clegg, associate professor of internal medicine and senior study author, University of Texas Southwestern Medical Center.
"We hadn`t previously thought of sex hormones as being critical regulators of food intake and body weight," added Clegg, reports the journal Cell Metabolism.
The researchers relied upon a mouse study, which is the first to show that estrogen, acting through two hypothalamic neural (cell) centres in the brain, keeps female body weight in check by regulating hunger and energy expenditure, according to a Texas statement.
The hypothalamus is a very small, but extremely important brain part involved in temperature regulation, control of food and water intake, sexual behaviour and reproduction, control of daily cycles in physiological state and behaviour and mediation of emotional responses.
Female mice lacking estrogen receptor alpha - a molecule that sends estrogen signals to neurons - became obese and developed related diseases, such as diabetes and heart disease.
Similar results were not seen in male mice, although researchers suspect other unknown estrogen receptor sites in the brain play a similar role in regulating metabolism for males as well.
The study could lead to new HRTs in which estrogen is delivered to specific parts of the brain that regulate body weight, thereby avoiding the risks associated with full-body estrogen delivery, such as breast cancer and stroke.