Assessing the effect of interaction between an FTO variant (rs9939609) and physical activity on obesity in 15,925 Swedish and 2,511 Finnish adults

Recent reports have suggested that genotypes at the FTO locus interact with physical activity to modify levels of obesity-related traits. We tested this hypothesis in two non-diabetic population-based cohorts, the first from southern Sweden and the second from the Botnia region of western Finland. In total 2,511 Finnish and 15,925 Swedish non-diabetic middle-aged adults were genotyped for the FTO rs9939609 variant. Physical activity was assessed by questionnaires and standard clinical procedures were conducted, including measures of height and weight and glucose regulation. Tests of gene x physical activity interaction were performed using linear interaction effects to determine whether the effect of this variant on BMI is modified by physical activity. The minor A allele at rs9939609 was associated with higher BMI in both cohorts, with the per allele difference in BMI being about 0.13 and 0.43 kg/m(2) in the Swedish and Finnish cohorts, respectively (p < 0.0001). The test of interaction between physical activity and the rs9939609 variant on BMI was not statistically significant after controlling for age and sex in either cohort (Sweden: p = 0.71, Finland: p = 0.18). The present report does not support the notion that physical activity modifies the effects of the FTO rs9939609 variant on obesity risk in the non-diabetic Swedish or Finnish adults studied here.