Exaggerated nutrient-stimulated GIP secretion is also observed in obese leptin-deficient ob/ob mice [327,328,340] and in humans with obesity [481,[497], [498], [499], [500]], but this has not been confirmed by other studies [492,[501], [502], [503], [504]]. The gene discussed is GIP; the disease is obesity due to melanocortin 4 receptor deficiency.