After the first classification of β-adrenoceptors (β-ARs) [1] and the identification of the third subtype, β3-AR, in 1989 [2], the attention of research studies focused on the involvement of β3-ARs in physiologic and pathologic conditions, with particular attention focused on cardiovascular disease, diabetes, obesity and cancer. Here, ADRB3 is linked to obesity due to melanocortin 4 receptor deficiency.