FTO and obesity due to melanocortin 4 receptor deficiency: Our results confirm previous findings of heterogeneity in genetic effects according to obesity sub-phenotype at variants in FTO and TCF7L2 [Cauchi et al., 2006, 2008; Freathy et al., 2008; Timpson et al., 2009], and highlight a potential novel T2D association that warrants follow-up in replication cohorts.