By using overlapping published linkage studies on obesity (Atwood et al., 2002), insulin secretion (Abney, Ober & McPeek, 2002; Duggirala et al., 2001) and type 2 diabetes (Demenais et al., 2003; Ehm et al., 2000; Ghosh et al., 2000; Xiang et al., 2004), the ENPP1 gene was picked for further analysis. This evidence concerns the gene ENPP1 and obesity due to melanocortin 4 receptor deficiency.