Mice with a mutation in the Clock or BMAL1 gene show phenotypes resembling the metabolic syndrome, including predisposition to obesity, hyperglycaemia, and hyperlipidaemia (Rudic et al., 2004; Shimba et al., 2005; Turek et al., 2005; Lamia et al., 2008). The gene discussed is CLOCK; the disease is obesity due to melanocortin 4 receptor deficiency.