The high methylation of the insulin-like growth factor 2 (IFG2) and H19 genes (IGF2/H19), serotonin transporter gene (SLC6A4), retinoid X receptor alpha (RXRalpha), endothelial nitric oxide synthase (eNOS), and trophoblast Cell Surface Antigen 2 gene (TACSTD2) at birth have been linked to subsequent obesity development, suggesting that locus-specific DNA methylation is established early in life but exerts its effects later on. This evidence concerns the gene NOS3 and obesity due to melanocortin 4 receptor deficiency.