23 September 2010
In 2005, according to the World Health Organisation, around 1.6 billion adults and a further 20 million children under the age of five were overweight across the world. By 2015, there are expected to be more than 700 million obese adults (increasing from 400 million in 2005). Although this epidemic has largely been driven by changes in lifestyle, such as the increase in availability of calorie-rich foods coupled with an increasingly sedentary lifestyle, recent genome-wide association studies (GWAS) have shown that genetic factors also play an important role. A study published in PLoS Medicine assesses how a physically active lifestyle impacts on an individual’s genetic predisposition to obesity [Li et al. (2010) PLoS Med 7(8):e1000332. doi:10.1371/journal.pmed.1000332].
Using a large population-based study design, Li et al. genotyped 12 SNPs in obesity susceptibility loci in 20,000 individuals of white European descent. These SNPs were then used to calculate a genetic predisposition score based on adding the number of BMI-increasing alleles across the 12 SNPs. Physical activity was assessed by means of a validated self-administered questionnaire, with data available for 20,000 individuals at baseline and 12,000 at a second health check 3-4 years later. Interactions between the genetic predisposition scores and levels of physical activity were then assessed based on obesity risk and changes in BMI over time.