Having a lower percentage of body fat may not always lower your risk for heart disease and diabetes, according to two scientists from the Institute for Aging Research of Hebrew SeniorLife, an affiliate of Harvard Medical School. The researchers have identified a gene that is linked with having less body fat, but also with an increased risk of type 2 diabetes and heart disease.
"We've uncovered a truly fascinating genetic story and, when we found the effect of this gene, we were very intrigued," says researcher Douglas P. Kiel. "People, particularly men, with a specific form of the gene are both more likely to have lower percent body fat, but also to develop heart disease and type 2 diabetes. In simple terms, it is not only overweight individuals who can be predisposed for these metabolic diseases."
Writing about their findings in Nature Genetics, the researchers explain how they examined the genomes of more than 75,000 people to look for the genes that determine body fat percentage. They found strong evidence for a gene, called IRS1, to be linked with having less body fat. But on further investigation, they found that this gene also leads to having unhealthy levels of cholesterol and blood glucose.
Apparently, the gene lowers only the "subcutaneous" fat under the skin, but not the more harmful "visceral" fat that surrounds organs. The study authors speculate that people with this gene variant are less able to store fat safely under the skin and may, therefore, store fat elsewhere in the body, where it may interfere with normal organ function.
"Genetic variants may not only determine the amount of total fat in your body," says Kiel, "but also what kind of fat you have. 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."
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Source: Hebrew SeniorLife Institute for Aging Research