MC4R plays a pivotal role in the regulation of body weight, as demonstrated in animal models and in humans, in which variants that cause a LoF by reducing cAMP production are associated with obesity (Farooqi et al., 2003; Hinney et al., 2006; Stutzmann et al., 2008). The gene discussed is MC4R; the disease is obesity due to melanocortin 4 receptor deficiency.