June 27, 2011 -- It's not how much fat you have, but where it's stored that may determine your health risk, according to a new study.
Researchers have isolated a gene in some people that is associated with low body fat but also a higher risk of heart disease and diabetes, especially among men.
"In simple terms, it is not only overweight individuals who can be predisposed for these metabolic diseases," researcher Douglas P. Kiel, MD, a professor of medicine at Harvard Medical School, says in a news release.
The study suggests that the gene lowers the fat found underneath the skin but not the more harmful fat that surrounds the organs.
"Genetic variants may not only determine the amount of total fat in your body, but also what kind of fat you have,” Kiel says. “Some collections of fat, such as the kind located just under the skin, may actually be less harmful than the type located in the abdominal cavity, which may increase the risk of developing metabolic disease."
In the study, published in Nature Genetics, researchers analyzed the genetic makeup of more than 75,000 people and looked at associations between body fat and the risk of metabolic diseases like heart disease and diabetes.
The results showed a variant of the gene IRS1 was strongly associated with low body fat and unhealthy levels of cholesterol and blood sugar, two risk factors for heart disease and diabetes.
Researchers say people with this gene may be less able to store fat safely under the skin and may store it elsewhere in the body, where it may interfere with normal organ function.
"The effect may be more pronounced in men due to the different body fat distributions between the sexes, Ruth Loos, MD, of the Medical Research Council in the U.K., says in a news release. "Men store less fat than women, so they are more sensitive to changes in its distribution."