Overall, this study demonstrated that a 20 h fast can induce significant steatosis in hCYP2B6-Tg mice, CYP2B6 in vivo elicits a strong sexually dimorphic response in lipid metabolism and liver steatosis which affects females more than males, and the oxylipins 9-HODE and 9-HOTrE are only a minor part of CYP2B6’s effects, leaving other oxylipins or lipid metabolites that most likely mediate its anti-obesity and steatotic effects. The gene discussed is CYP2B6; the disease is steatosis.