UCP1 and obesity due to melanocortin 4 receptor deficiency: To gain mechanistic insights of the EPA effects on SAT thermogenesis and how UCP1 controls obesity resistance temperature-dependently, in the current study, we used WT and UCP1 KO male mice housed at either ambient or thermoneutral environments and supplemented with high-fat diets (HFD) with or without EPA-enriched fish oil.