Furthermore, plasma ghrelin levels have been reported to be reduced in animal models of obesity (Ariyasu et al., 2002; Levin et al., 2003) and in obese subjects, being inversely correlated with adiposity, fasting insulin, and leptin (Tschop et al., 2001). The gene discussed is GHRL; the disease is obesity due to melanocortin 4 receptor deficiency.