Dietary excesses and also host genetic factors are the main obesity causes in humans5, with heritability estimates ranging from 0.40 to 0.70 in humans6 and farm animals7,8, and some loci already identified for obesity (e.g., MC4R, leptin, Fob, and FTO)9–11 and obesity-related metabolic disorders (NOD1,212, apolipoprotein E13,14, and CD1415). Here, FTO is linked to obesity due to melanocortin 4 receptor deficiency.