Is MC4R useful for blood sugar?

MC4R (melanocortin-4 receptor) is primarily known for appetite regulation and energy homeostasis. Some GWAS studies show weak associations with fasting glucose and insulin resistance, but effects are small and indirect (e.g., via BMI). Rare monogenic MC4R mutations cause severe obesity, which secondarily affects blood sugar. For everyday blood sugar management in healthy individuals, MC4R is not clinically useful. Evidence is mostly GWAS-based with moderate effect sizes. A DNA test for MC4R polymorphisms does not yield actionable recommendations for glucose control. Lifestyle, diet, and continuous glucose monitoring (CGM) are far more informative. Beware of overblown marketing claims: MC4R is not a 'blood sugar gene' in a personalized diet sense.