We looked for effects of AIF1 on macrophage polarization in adipose tissue and obesity-associated insulin resistance, and found no significant differences in M1 vs. M2 marker expression in BAT from WT and Aif1−/− mice fed CD or HFD; circulating adipokines including adiponectin and resistin were also not different (Supplementary Fig. 12a, b, e). Here, RETN is linked to obesity due to melanocortin 4 receptor deficiency.