"One of the most exciting parts of this work is that most of the BMI-associated variants identified are in or near genes that have never before been connected to obesity. Through this work we are discovering that the underlying biological underpinnings of obesity are many, varied and largely uncharacterized," says Elizabeth K. Speliotes, MD, PhD, MPH, of Massachusetts General Hospital and the Broad Institute, the first author of the BMI study and also involved in both studies.
Although the effects of each individual variant were modest, individuals who carried more than 38 BMI-increasing variants were on average 15 to 20 pounds heavier than those who carried fewer than 22 such variants. However, even in combination these variants explain only a small fraction of the overall variation in body weight. The researchers found that the combined genetic information from these variants was only slightly better than flipping a coin in predicting whether an individual would be obese, probably because many other factors, both genetic and environmental, contribute to overall weight.
The second study looked at genetic associations with how fat is distributed in the body.
Studies have shown that fat stored in the abdomen increases the risk of type 2 diabetes and heart disease, even after adjusting for obesity. In contrast, fat stored in the hips and thighs may actually protect against diabetes and high blood pressure. The investigators examined the genetic determinants of waist-to-hip ratio, a measure of fat distribution, analyzing data from 77,000 participants in 32 studies. The regions identified in this analysis were then checked against data from another 29 studies including over 113,500 individuals. This revealed 14 gene regions associated with waist-to-hip ratio, adding 13 new regions and confirming the one previously known association.
|Contact: Mike Morrison|
Massachusetts General Hospital