CLOCK and obesity due to melanocortin 4 receptor deficiency: Numerous single nucleotide polymorphisms (SNPs) in human clock genes, including rs18012602, rs4580704, rs4864584, rs3749474 and rs1464490, have also been associated with obesity (Sookoian et al., 2008), hyperglycaemia, and a higher prevalence of T2D (Sookoian et al., 2008).