ADRB2 and obesity due to melanocortin 4 receptor deficiency: The PubMed (1950–2014), Embase (1974–2014), and China National Knowledge Infrastructure (CNKI, 1994–2014) databases were searched using the search terms (“Beta2-adrenergic receptor”, “β2-adrenergic receptor” or “ADRB2”), “polymorphism,” and “obesity”.