Tuesday, August 31, 2010

Is obesity genetic?

While lifestyle contributes substantially more to risk of cancer (and other chronic diseases) than genetics alone, the interplay between genetics and lifestyle is a subject of increasing interest. That's what makes a new study out of the UK, published in PLoS Medicine so exciting.

The researchers took 12 genetic mutations that had previously been found to be associated with obesity risk and examined how they combined to be associated with risk of weight gain. The presence of each additional mutation increased risk of weight gain -- the more mutations, the greater the risk. The mutations significantly increased the risk of obesity by 16%. The researchers then did something quite novel, using the data the participants reported about how physically active (or not) they were, the researchers re-examined the associations. In the inactive men and women, the association was stronger than in the inactive people. What this means is that the effect of genes were stronger in the people who were inactive - or - that physical activity "erased" some of the genetic predisposition - about 40% of it.

What does this mean for those of us who have no idea how "genetically predisposed" we might be to obesity? Physical activity has benefits for everyone, but for individuals who are genetically predisposed to obesity, physical activity is especially important. It also means that a genetic predisposition to obesity isn't cause for "doom and gloom" - there ARE things you can do to counter it - notably, being physically active!

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