Walking briskly for an hour a day could cut by half the effect of sedentary lifestyle behaviors on a person’s genetic tendency towards obesity, according to a study presented at the American Heart Association’s Epidemiology and Prevention/Nutrition, Physical Activity and Metabolism 2012 Scientific Sessions.
According to the lead author, Qibin Qi, PhD, a post-doctorate research fellow in the Department of Nutrition at Harvard School of Public Health, the average American watches between 4 and 6 hours of television a day. This type of behavior can worsen a person’s genetic predisposition to become obese.
“While previous studies have looked at how physical activity affects genetic predispositions, this is the first study that directly looked at the effect of the sedentary behavior of television watching on the body mass index (BMI) of individuals with a genetic predisposition to obesity,” Qi stated in a press release.
The study included 7,740 women and 4,564 men from the Nurses’ Health Study and Health Professionals Follow-up Study. The researchers collected data on the participants’ physical activity and TV watching 2 years prior to assessing BMI.
They then calculated a genetic predisposition score based on 32 established BMI-predisposing genetic variants. The effect of genes on obesity was measured by differences in BMI per point of the genetic predisposition score, corresponding to each BMI-increasing gene.
The effect of each BMI-increasing gene was reduced in people with the highest level of physical activity, while the genetic effect was more pronounced in people who spent 40 hours a week watching television. Genetic testing is not currently available to the general public yet, but Qi advised physicians to ask patients about a family history of obesity. He also said it is unclear how these genes affects BMI.
“These genes were just identified in the past 5 years, and the exact functions of the genetic variants are still unknown. Future studies will be needed to uncover the underlying mechanisms,” he stated.