15 March 2012

Walking Off The Influence of "Thrifty Genes"

"I can't help it, it's my genes" is a familiar phrase among frustrated dieters and gym goers who feel they can’t make the scale budge despite all efforts to reduce calories and exercise more. There may be something to their justification. After all, weight can depend partly on genetic makeup (among several other factors).

Luckily, the genetic revolution continues to churn out exciting news giving us hope that, no, we're not completely left at the mercy of the wrong kind of genes. The latest example is a study presented March 14 at the American Heart Association meeting in San Diego. The study found that people could keep their obesity genes under wraps by doing as little as turning off the tube and taking a brisk walk.

The study found that a brisk one-hour walk daily cut the influence of genes on obesity by as much as half! On the other hand, every couple of hours of watching television appeared to increase the influence of obesity genes by a quarter. That can make a major difference for the average American who watches TV for four to six hours a day.

To identify individuals for their study, the researchers determined genetic predisposition score based on more than 30 genetic variants in 7,740 women and 4,564 men from the Nurses' Health Study and Health Professionals Follow-up Study. Each variant had been previously established to have an influence on body mass index (BMI), a ratio based on an individual's height and weight used as criteria for determining overweight and obesity. 

How do genes affect weight exactly? The mechanisms aren't yet clear, say the researchers, but a look at humanity's evolved past could offer some clues. The "thrifty gene" theory, for example, has it that the human body hasn’t changed much in the last 50 thousand years. The situation back then was quite different from the days of food aplenty today—in those near-famine times, our ancestors used up a lot of energy and time just searching for food, and they often went without.

A set of "thrifty genes" may have once served our ancestors to stockpile fat for use when calories were scarce. Unfortunately, those same genes in a person today can mean a serious disadvantage for shedding unwanted pounds and inches. 

While genetic screening for obesity isn't available for everyone yet, it doesn't mean that people, especially those who know they have a family history of obesity, can't make use of this study's findings right away. Since our hunter-gatherer ancestors often sought out food by making long, cross-country treks, it's only sensible that the same kind of behavior today—brisk walking an hour or more a day—could lead to the release of fat.

Matt McMillen writes more about the research presented at AHA's meeting in Health Magazine and republished in CNN's The Chart.  


American Heart Association Walking may lessen the influence of genes on obesity by half. March 2012. Retrieved March 15, 2012, from http://newsroom.heart.org/pr/aha/walking-may-lessen-the-influence-230079.aspx

Debusk R & Joffe Y. (2006) It's Not Just Your Genes! San Diego: BKDR. 

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