However, vagal CCK resistance during obesity could also be due to obesity-associated leptin resistance, as the leptin receptor is co-expressed with CCK-1R in the vagal afferent neurons65 and leptin potentiates the suppressive effect of CCK on appetite and increases vagal afferent activation following CCK administration66,67. The gene discussed is CCKAR; the disease is obesity due to melanocortin 4 receptor deficiency.