The Effect of FTO rs9939609 Gene Polymorphism on Exercise-Induced Fat Oxidation

Background The FTO rs9939609 polymorphism is well-studied for obesity and metabolism, but its effect on exercise-induced substrate oxidation remains unclear. This study aimed to examine the impact of the FTO rs9939609 polymorphism on fat oxidation (FAT), carbohydrate oxidation (CHO), and respiratory exchange ratio (RER) during and after exercise in sedentary young adult males. Methods A total of 45 male participants were recruited and genotyped for FTO rs9939609. Participants underwent an incremental treadmill exercise test, during which RER, FAT, and CHO oxidation rates were measured using indirect calorimetry. Substrate oxidation was assessed during both exercise and a 15-minute post-exercise recovery period. Data was analyzed according to recessive and dominant genetic models. Results The AA genotype group exhibited a significantly lower RER during compared to the AT + TT group, indicating a greater reliance on fat oxidation. Similarly, AA carriers had higher fat oxidation than AT + TT, while carbohydrate oxidation was significantly lower in AA compared to AT + TT. This trend persisted in the post-exercise recovery phase, with AA individuals maintaining higher fat oxidation and lower RER, though differences were less pronounced. Conclusion The findings suggest that the FTO rs9939609 polymorphism influences substrate oxidation in a recessive manner. AA genotype carriers oxidize fat over carbohydrates during moderate-intensity exercise and post-exercise recovery, while individuals with at least one T allele exhibit higher carbohydrate utilization. These results imply that genetic factors may play a role in metabolic responses to exercise. Future studies with larger, diverse populations and longitudinal training interventions are needed to confirm these findings.