PM20D1 and obesity due to melanocortin 4 receptor deficiency: Interventions that promote bidirectional changes in BAT Pm20d1 shift the metabolic phenotypes; so, BALB/c under partial inhibition of Pm20d1 becomes obesity prone and cold-intolerant, whereas C57BL/6 under increased expression of Pm20d1 presents reduced body mass gain and becomes cold-tolerant.