Evidence check: FTO in the context of Sport

FTO (fat mass and obesity-associated) gene variants, particularly rs9939609, are among the most robustly replicated genetic markers for body mass index and obesity risk in large GWAS. In the context of sport, the relevance is indirect: higher BMI or adiposity can affect performance in weight-dependent sports (e.g., endurance running, gymnastics) and may influence recovery and injury risk. Some studies have examined whether FTO genotype modifies the effect of exercise on weight loss or body composition changes, with mixed results. A meta-analysis found that physical activity can attenuate the genetic risk of obesity from FTO, but the interaction is small. For elite athletes, FTO is not a strong predictor of performance; other genes (e.g., ACTN3, PPARGC1A) have more direct links. Consumer DNA tests often include FTO in their reports, but the practical utility for sport nutrition or training is limited. The effect sizes are small, and lifestyle factors (diet, training volume, sleep) dominate. Therefore, while FTO provides some insight into genetic predisposition for body weight, it should not be overinterpreted for sport optimization. Evidence level: GWAS-based, with some human intervention studies showing modest interaction. Caveat: not diagnostic or prescriptive for athletic performance.