Using two genetic mouse models of CK1ε disruption (i.e., knock-out CK1ε−/− null mice and knock-in CK1εtau/tau mutant mice) under different diet conditions, we have demonstrated distinct effects of the circadian clock gene CK1ε on body weight regulation and susceptibility to excess weight gain induced by HF diet. The gene discussed is CLOCK; the disease is hydrops fetalis.