The impact of obesity on skeletal muscle maintenance and physiology has been addressed in rodent models of obesity, including leptin-deficient Lepob/ob mice (commonly termed “ob/ob”), leptin receptor-deficient Leprdb/db mice (termed “db/db”) and obese Zucker rats (which also have a leptin receptor mutation) (Kurtz et al., 1989; Tschop and Heiman, 2001), as well as in mice and rats fed a high-fat diet. The gene discussed is LEP; the disease is obesity due to melanocortin 4 receptor deficiency.