Populations as a whole can benefit from a physically active lifestyle, and those individuals with a genetic predisposition to obesity can benefit even more. Ruth J. F. Loos, from the Medical Research Council Epidemiology Unit (United Kingdom), and colleagues engaged data collected on 20,430 men and women enrolled in the European Prospective Investigation of Cancer (EPIC)-Norfolk study, examining 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 of the study subjects. The researchers then used modeling 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 team 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 that the size of this effect was greater in inactive people than in active people. In individuals who had a physically active lifestyle, this increase was only 379 g/variant, or 36% lower than in physically inactive individuals in whom the increase was 592 g/variant. Concluding that: “Our study shows that living a physically active lifestyle is associated with a 40% reduction in the genetic predisposition to common obesity,“ the team suggests that these findings challenge deterministic views of the genetic predisposition to obesity.