Genetic risk factors for obesity include both psychology-related gene polymorphisms including the S variant of 5-HTTPLPR and metabolism-related gene polymorphisms, including the R variant of β3-adrenergic receptor (β3AR, rs4994, W64R) [23,24] and the G variant of uncoupling protein 1 (UCP1, rs1800592, A3826G) [25,26]. Here, ADRB3 is linked to obesity due to melanocortin 4 receptor deficiency.