OXT and obesity due to melanocortin 4 receptor deficiency: Recently, and about 10 years after these first discoveries, three different studies have been published by Yuan et al. [23], Sun et al. [24], Conte et al. [19], each of them presenting a different theory on the role of Oxt in the regulation of energy metabolism and the paradox of normophagic obesity that we first described for Oxt−/− and Oxtr−/− mice [15,16].