LEPR and obesity due to melanocortin 4 receptor deficiency: The role of obesity on skeletal muscle physiology, structural maintenance, and regeneration after exposure to myotoxins or freezing has been analyzed in several obese animal models, such as: leptin-deficient (ob/ob), leptin receptor-deficient (db/db) mice, POUND (Leprdb/lb) mice lacking all functional leptin receptors, obese Zucker rats bearing a mutation in the leptin receptor, as well as in rodents fed a high-fat diet (HFD).