FTO and obesity due to melanocortin 4 receptor deficiency: Previously, a large amount of studies (Frayling et al., 2007; Heard-Costa et al., 2009; Lindgren et al., 2009; Meyre et al., 2009; Thorleifsson et al., 2009; Willer et al., 2009; Heid et al., 2010; Speliotes et al., 2010; Bradfield et al., 2012; Wen et al., 2012; Berndt et al., 2013; Monda et al., 2013; Locke et al., 2015; Shungin et al., 2015) have covered that FTO contributes to the risk of obesity due to the population-based studies and the relevant experiments elaborating specific mechanisms.