PPARGC1A and obesity due to melanocortin 4 receptor deficiency: Based on these observations we hypothesized that carnitine supplementation through inducing PGC-1α and PPARδ in skeletal muscle counteracts obesity and/or diabetes-induced muscle fiber transition from type I to type II and restores the muscle fiber distribution and the muscle oxidative metabolic phenotype observed during non-obese and non-diabetic states.