UCP1 and obesity due to melanocortin 4 receptor deficiency: HFD-fed total body IFNAR−/− mice and WT mice exhibited similar obesity as assessed by lack of differential total body weight (Fig. 4c; in agreement with a recent report13), energy expenditure, food intake, systemic cholesterol, total body adiposity, BAT Ucp-1 expression and WAT gross morphological appearance (Supplementary Fig. 6a−f).