What role does FUT2 play in weight loss?

FUT2's role in weight loss is indirect and not strongly supported. The gene encodes a fucosyltransferase that determines secretor status—whether ABO antigens are secreted into bodily fluids. This influences gut microbiome composition, as some bacteria feed on these antigens. Non-secretors (FUT2 null variants) tend to have lower Bifidobacterium levels, which may affect nutrient absorption and energy metabolism. However, evidence for a direct causal link to weight loss is weak and inconsistent. Weight loss is primarily driven by calorie balance, diet, and exercise. A FUT2 test alone is not clinically actionable for weight management. Evidence grade: mechanistic / human-moderate. Caveat: Do not base diet or supplement decisions solely on this gene.