At 12 weeks of age, ob/ob (OB) mice presented a marked obesity (Fig. S1A), hyperglycemia (Fig. S1B), liver steatosis (Fig. S1C), and altered insulin-induced AKT phosphorylation in Gast, compared to wild type (WT) littermates (Fig. S1D). Here, AKT1 is linked to obesity due to melanocortin 4 receptor deficiency.