ADRB2 and obesity due to melanocortin 4 receptor deficiency: For example, the adrenergic receptor beta-2 (ADRB2), adrenergic receptor beta-3 (ADRB3), guanine nucleotide-binding protein (GNB3), uncoupling protein 1 (UCP1), and fat mass- and obesity-associated (FTO) genes are all reported to have associations with obesity.