While all adults suffer mental decline with age, playing sport, going to the gym or even just a brisk walk with the dog can help protect the brain, scientists said. Picture: Lulama Zenzile

A sedentary lifestyle can amplify a genetic disposition to obesity, but just walking briskly each day can cut that effect in half, a new study has shown.

“This is the first study that directly looked at the effect of the sedentary behaviour of television watching on the body mass index (BMI) of individuals with a genetic predisposition to obesity,” said study author Qibin Qi authors at a conference by the American Heart Association this week in San Diego, California.

To combat the results, Qi said a one-hour daily walk “reduced the genetic influence towards obesity, measured by differences in BMI by half.”

The study involved 7,740 women and 4,564 men, with researchers collecting data on their physical activity and TV watching two years prior to assessing their BMI.

The average American watches television for about four to six hours each day, noted Qi.

The BMI indicator is the ratio of weight in kilograms to square of height in meters - on this scale, a score of 30 or more is considered obese.

The genetic effect on BMI was seen as “more pronounced in people who spent 40 hours a week watching television than those who spent an hour or less, 0.34 versus 0.08 kg/m2,” according to the study.

The recommended walking exercise was associated with 0.06 kg/m2 reduction in the genetic effect on BMI, said researchers, who presented their report at the American Heart Association's Epidemiology and Prevention/Nutrition, Physical Activity and Metabolism 2012 Scientific Sessions conference in San Diego. - AFP