These 6 polymorphisms of SIRT1 have been widely investigated mainly in the context of metabolism and have been found to be associated with the risk of obesity (rs10509291, rs33957861, and rs1467568) [32,42,43] and carbohydrate metabolism disturbances (rs10509291 and rs1467568) [44,45]. Here, SIRT1 is linked to obesity due to melanocortin 4 receptor deficiency.