GATM and obesity due to melanocortin 4 receptor deficiency: Moreover, depleting creatine levels in thermogenic adipocytes of mice by deleting the rate-limiting enzyme of creatine biosynthesis, glycine amidinotransferase (GATM), impairs energy expenditure due to reduced thermogenesis and causes diet-induced obesity [67, 68]. The existence of this cycle in BAT supports the concept that increasing mitochondrial ATP synthesis can be used as an approach to promote energy dissipation.