Twelve studies examined the association between the UCP2 -866G/A polymorphism and obesity risk [11]–[22], nine studies for the UCP2 Ala55Val polymorphism [16], [22]–[29] and eight for the UCP3 -55C/T polymorphism [15]–[17], [28]–[32]. This evidence concerns the gene UCP2 and obesity due to melanocortin 4 receptor deficiency.