Why Does Fat Go to a Man's Belly and a Women's Hips and Thighs?
In general, men tend to become apple-shaped, storing their fat in the abdominal areas, but maintain normal hips and thighs. Women on the other hand, tend to become pear-shaped, storing their fat lower down in their hips and thighs. Why is this? For research Steven R. Smith, M.D., director at the Sanford-Burnham Translation Research Institute for Metabolism and Diabetes, this simple truth was worth investigating. He found that the placement of fat storage in the body is genetic. Furthermore, belly fat is associated with higher risks of heart disease and diabetes, while hip and thigh fat is not.
To come to these conclusions, Smith and his colleagues first took fat samples from men and women, and they compared the genes most active in belly fat to those most active in thigh fat. They uncovered huge differences. There were 125 genes in the man's fat which were expressed differently in the belly from those in the thighs. For women, there were 218 genes expressed differently, most of which are unique to women.
Their most notable difference were in the homeobox genes, genes known for their role in shaping a developing embryo. They determine which cells and organs go where. Many of these homeobox genes are influenced by hormones like estrogen. "We believe these genes actually program those fat cells to respond differently to different hormones and other signals," Smith says.
Smith and his team also isolated stem cells from belly and thigh fat, and grew them in laboratory petri dishes. Even when grown under controlled conditions, the same location-specific differences in gene activity were observed. The researchers could then conclude that the fat cells are pre-programmed, genetically destined for their final location.
"Even though many women hate having large hips and thighs, that pear shape actually reduces their risk of heart disease and diabetes. In fact, women who have heart attacks tend to have more belly fat than thigh fat."
This research marks a new way of thinking. "Most people want to stop belly fat. But the problem is not just the fat—it's the location. Belly fat is just a marker of the problem. The real issue is in inability to store that fat on the hips and thighs," he continues.
This study was published in the Journal of Clinical Endocrinology and Metabolism
Fat Belly image via Shutterstock