Is CYP2D6 useful for weight loss?

CYP2D6 is a cytochrome P450 enzyme primarily involved in drug metabolism, not in energy expenditure or fat oxidation. Some direct-to-consumer DNA tests market CYP2D6 variants as relevant for weight loss, but the scientific evidence is very weak. No robust studies demonstrate that CYP2D6 polymorphisms directly affect weight loss outcomes. Any indirect links come from its role in metabolizing medications (e.g., certain antidepressants or beta-blockers) that may influence body weight, but this is not a basis for diet or exercise personalization. Claims that a DNA test can tailor a weight loss plan based on CYP2D6 are largely marketing hype. Caloric balance, macronutrient composition, physical activity, and sleep are far more impactful. CYP2D6 testing is useful in pharmacogenetics, not for weight management. Evidence: marketing/unclear. Caveat: no clinical validation for this purpose.