Mice with a truncated exon 18 and deleted exon 19 of the Clock gene (Clock Δ19 mice) have a greatly attenuated diurnal feeding rhythm, are hyperphagic and obese, and develop a metabolic syndrome of hyperleptinemia, hyperlipidemia, hepatic steatosis, and hyperglycemia [5]. The gene discussed is CLOCK; the disease is hyperlipidemia.