Supplementary Material for: <b><i>FTO</i></b> Genotype Interacts with Improvement in Aerobic Fitness on Body Weight Loss During Lifestyle Intervention

<b><i>Objective:</i></b> Not every participant responds with a comparable body weight loss to lifestyle intervention, despite the same compliance. Genetic factors may explain parts of this difference. Variation in fat mass and obesity-associated gene (<i>FTO</i>) is the strongest common genetic determinant of body weight. The aim of the present study was to evaluate the impact of <i>FTO </i>genotype differences in the link between improvement of fitness and reduction of body weight during a lifestyle intervention. <b><i>Methods:</i></b> We genotyped 292 healthy subjects for <i>FTO </i>rs8050136. Participants underwent a 9-month lifestyle intervention. Before and after intervention, aerobic fitness was tested by bicycle (VO<sub>2</sub>max) and treadmill spiroergometry (individual anaerobic threshold (IAT), subgroup of N = 192). <b><i>Results:</i></b> Participants lost body weight (p < 0.0001) independent of <i>FTO</i> genotype (p = 0.5). There was a significant correlation between improvement in VO<sub>2</sub>max and decrease in body weight (p < 0.0001). <i>FTO</i> genotype interacted with this relationship (p = 0.0042 for VO<sub>2</sub>max, p = 0.0049 for IAT). When stratifying the cohort according to their improvement in VO<sub>2</sub>max, <i>FTO</i> obesity-risk A-allele carriers in the higher quartiles of improvement in fitness lost significantly less body weight. <b><i>Conclusions:</i></b> Our data reveal that genetic variation in <i>FTO</i> impacts on body weight reduction during lifestyle intervention only in subjects with marked improvement in aerobic fitness.