Although this finding is reminiscent of the negative correlations between METRNL levels and visceral adiposity found in adults with obesity and/or type 2 diabetes (12, 13), the fact that it occurs only at birth indicates the need for future studies to explore a possible involvement of METRNL in the fat accretion occurring during late fetal development, something totally unknown to date. Here, METRNL is linked to obesity due to melanocortin 4 receptor deficiency.