FGF21 and obesity due to melanocortin 4 receptor deficiency: Of note, a recent study showed by using adipocyte‐specific β‐klotho (Klb) receptor knockout mice that BAT mediates the glucose‐lowering effect of FGF21, whereas the anti‐obesity effect of FGF21 appears to be through non‐adipose tissues (Bon Durant et al, 2017).