Abnormal DNA methylations of key metabolic-related genes, such as Leptin (Houde et al, 2015), adiponectin (Houde et al, 2015), PGC1α (Brons et al, 2010), IGF-2 (Perkins et al, 2012), appetite-related genes-(POMC (Crujeiras et al, 2013), NPY (Crujeiras et al, 2013)), are frequently implicated in the development of obesity and insulin resistance. This evidence concerns the gene IGF2 and obesity due to melanocortin 4 receptor deficiency.