Evidence check: MC4R in the context of weight loss

MC4R (melanocortin-4 receptor) is a key regulator of appetite and energy balance. Rare, highly penetrant mutations cause monogenic obesity with severe hyperphagia – evidence is human-strong. However, most consumer DNA tests analyze common variants (e.g., rs17782313) with very small effect sizes. Studies show that carriers of such variants have a slightly increased risk of overweight, but the impact on weight loss through diet or exercise is small and inconsistent. Clinical predictive power is weak; a positive result does not warrant specific therapy. Evidence for common SNPs is human-moderate (GWAS, meta-analyses). Important: MC4R tests are not diagnostic and do not replace medical evaluation for obesity. Safety note: Do not initiate extreme diets or supplements based solely on a genetic test.