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

The recommended walking exercise was associated with 0.06 kg/m2 reduction in the genetic effect on BMI, researchers said

“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 at a conference by the American Heart Association in San Diego, California.

To combat the results, Dr 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 Dr Qi.

The BMI indicator is the ratio of weight in kilograms to square of height in metres – 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, researchers said.