What role does FTO play in fatigue?

FTO (fat mass and obesity-associated gene) is primarily linked to body weight and fat mass. GWAS studies show that certain variants (e.g., rs9939609) are associated with a slightly higher BMI and increased obesity risk. A direct causal role in fatigue is not established. If FTO variants contribute to weight gain via increased calorie intake or altered food preferences, this could indirectly lead to fatigue – for example through sleep apnea or metabolic strain. However, the effect size of single SNPs is very small and insufficient for personalized fatigue assessment. Direct-to-consumer tests often overstate the clinical relevance of such variants. For unexplained fatigue, other causes (iron deficiency, thyroid function, sleep quality) should be prioritized.