In humans, various CLOCK single nucleotide polymorphisms (SNPs) (i.e. rs1464490, rs3749474, rs4864584, rs4580704 and rs18012602) have also been associated with obesity [34–36], hyperglycemia and greater prevalence of T2D in cross-sectional studies [36, 37]. Here, CLOCK is linked to obesity due to melanocortin 4 receptor deficiency.