New findings from a study suggest that the genetic predisposition to obesity can be reduced by an average of 40 per cent through increased physical activity. Although the whole population can benefit from a physically active lifestyle, in part through reduced obesity risk, the study shows that individuals with a genetic predisposition to obesity can benefit even more. The study was published in PLoS Medicine

The authors used a cohort study of 20,430 people living in Norwich, UK and examined 12 different genetic variants which are known to increase the risk of obesity. The researchers tested how many of these variants each study participants had inherited from either parent.

They then assessed the overall genetic susceptibility to obesity by summing the number of variants inherited into a ‘genetic predisposition score.'

Most individuals inherited between 10 and 13 variants, but some had inherited more than 17 variants, while others fewer than 6. In addition the researchers assessed occupational and leisure-time physical activities in each individual by using a validated self-administered questionnaire.

The researchers then used modelling techniques to examine whether a higher ‘genetic predisposition score' was associated with a higher body mass index (BMI)/obesity risk and, most importantly, they also tested whether a physically active lifestyle could attenuate the genetic influence on BMI and obesity risk.

The researchers found that each additional genetic variant in the score was associated with an increase in BMI equivalent to 445g in body weight for a person 1.70 m tall, and the size of this effect was greater in inactive people than in active people.

Furthermore, in the total sample each additional obesity-susceptibility variant increased the odds of obesity by 1.1-fold.

However, the increased odds per variant for obesity risk were 40 per cent lower in physically active individuals compared to physically inactive individuals.