The β1- and β2-adrenoceptors (Gs-coupled), and β2a-adrenoceptors (Gi-coupled) coexist in human fat cells, where they activate and inhibit lipolysis, respectively.37 The 825T allele of the GNB3 gene appears to decrease the production of GNB3 in fat cells and thereby inhibit lipolysis via β1-, β2-, and β2a-adrenoceptor signaling.37 From a study of post-pregnancy weight retention, Gutersohn et al.28 reported that subjects with a GNB3 825 T/T genotype are at high risk for obesity and post-pregnancy weight retention if they do not exercise regularly. Here, GNB3 is linked to obesity due to melanocortin 4 receptor deficiency.