We observed a significant effect of the FTO×PA interaction on waist circumference (betainteraction = −0.33 cm, p interaction = 0.002) and body fat percentage (betainteraction = −0.19%, p interaction = 0.02) (Table 2; Figures S4 and S5). The influence of the FTO risk allele on waist circumference was 33% smaller and the influence on body fat percentage 36% smaller in physically active individuals than in inactive individuals (Table 2). Similar to the results for BMI, the effect of the FTO×PA interaction on waist circumference was also more pronounced in North American populations (betainteraction = −1.02 cm) than in Europeans (betainteraction = −0.22 cm) (p difference = 0.01) (Table 2; Figure S4). We found a similar difference for body fat percentage (betainteraction = −1.57% in North Americans versus betainteraction = −0.18% in Europeans) that, however, did not reach significance (p difference = 0.1), but few North American individuals had data on body fat percentage (n = 892) (Table 2; Figure S5).
