MC4R and obesity due to melanocortin 4 receptor deficiency: Voluntary access to running wheels or running activity ameliorates hyperphagia and obesity of Otsuka Long-Evans Tokushima Fatty (OLETF) rats lacking cholecystokinin (CCK) 1 receptors (Bi et al., 2005); chronic exercise lowers the defended body weight and adiposity in diet-induced obese (DIO) rats (Levin and Dunn-Meynell, 2004); and voluntary exercise delays monogenetic obesity and overcomes reproductive dysfunction of melanocortin-4 receptor (MC4R) knockout mice (Irani et al., 2005).