The number of mitochondria present, along with their form and function, are highly tissue-dependent.[8,20,21] Brown adipose tissue (BAT) is rich in mitochondria, which are integral in the process of thermogenesis.[22] Brown adipocytes produce heat primarily through the uncoupling of the cristae’s proton gradient, which is facilitated through uncoupling protein 1 (UCP1).[23] In both rodent and human models, a decrease in BAT thermogenic function has been observed with advanced aging and has been associated with the development of metabolic disorders, including obesity and diabetes. The gene discussed is UCP1; the disease is obesity due to melanocortin 4 receptor deficiency.