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Research Reveals Genes That Affect Obesity and Where the Extra Fat Goes

Oct. 11, 2010 -- Your genes may influence how you look in your skinny jeans.

Two studies have identified 18 new genes linked to overall obesity and 13 more that influence whether your weight goes to your belly or to your thighs.

The findings come from the Genetic Investigation of Anthropomeric Traits (GIANT) consortium and appear in Nature Genetics; if validated, they may play a role in how obesity is categorized and treated.

In the first study, researchers conducted an analysis of 46 studies of 123,865 people and identified 18 new genetic regions associated with body mass index (BMI). They also confirmed 14 regions that had been noted before. Some of these genes affect appetite control and others may play a role in metabolism.

The more obesity genes a person had, the greater their risk of being obese, the study showed. Individuals who carried 38 or more BMI-associated genes weighed 15 to 20 pounds more, on average, than those who had fewer than 22, the researchers report. Still, these variants explain only a small fraction of the overall variation in body weight because many other genetic and environmental factors also contribute to obesity risk.

In the second study, researchers analyzed 32 studies of 77,167 people to identify genes associated with hip-to-waist ratio, which is a measure of body fat distribution. Belly fat is a known risk factor for type 2 diabetes and heart disease, while fat stored in the hips and thighs may actually be protective against diabetes and high blood pressure.

This study yielded 13 novel genes, and of these, seven genes had a more pronounced effect among women.

Why Diets Don't Always Work

"We know that 50% of our predisposition to weight is genetic and our study is trying to uncover the underpinnings of this," says Elizabeth K. Speliotes, MD, PhD, MPH, an instructor of medicine and gastroenterology at Massachusetts General Hospital and a fellow at the Broad institute in Boston.

The new findings may help explain why blanket recommendations about exercise and eating right just don’t work for a lot of people, she says.

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