Genetic deficiency of either PrRP or GPR10 results in late-onset obesity and the loss of anorectic responses to CCK (Bechtold and Luckman, 2006, Gu et al., 2004, Takayanagi et al., 2008, Watanabe et al., 2005). Here, CCK is linked to obesity due to melanocortin 4 receptor deficiency.