Finally, the reduced lipid levels in Park2 KO mouse livers were associated with increased activation of the cellular energy sensor AMP kinase (AMPK), suggesting that the negative energy balance that contributed to protection from obesity during chronic HFD feeding in the Park2 KO mice manifested at the level of the hepatocyte during short‐term HFD feeding and contributed to the improved hepatic insulin sensitivity. The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.