The decreased expression of SIRT1 is related to obesity [162] and genetic variants located in the SIRT1 gene have been associated with body mass index (BMI) and obesity risk; specifically, a lower BMI has been observed in carriers of the minor alleles of rs7895833 (G) and rs1467568 (A) [161]. This evidence concerns the gene SIRT1 and obesity due to melanocortin 4 receptor deficiency.