CLOCK and digestive system neoplasm: In this context, clock mutant mice, as other genetically modified (knockout and transgene) animal models in clock genes, are obese due to hypertrophied visceral adipose tissue, together with liver steatosis, hyperglycemia, hyperinsulinemia, hypertriglyceridemia and hyperleptinemia, which, overall, resemble (human) metabolic syndrome [8,9].