Is FTO useful for fatigue?

Whether the FTO gene is useful for fatigue requires a nuanced answer. FTO (fat mass and obesity-associated) is primarily linked to obesity and BMI via large GWAS. Some studies have reported weak associations between FTO variants and fatigue or reduced physical activity, but these are largely mediated by BMI or metabolic health. The effect sizes are small and not clinically actionable. Fatigue is a multifactorial symptom with many potential causes (iron deficiency, thyroid dysfunction, sleep disorders, mental health, chronic inflammation). A DNA test for FTO does not provide meaningful information for fatigue assessment. The evidence is mechanistic/unclear: no validated predictive models exist. For fatigue workup, standard lab tests (CBC, ferritin, TSH, vitamin D, B12) and clinical evaluation are far more informative. A consumer FTO result should not guide decisions about further testing. Safety note: persistent fatigue warrants medical evaluation, not reliance on genetic tests.