Pharmacological treatment with FGF21 ameliorates age‐related metabolic disorders such as insulin resistance, dyslipidemia, and obesity in rodents (Coskun et al., 2008; Kharitonenkov et al., 2005), and pilot studies in humans indicate that treatment with an FGF21‐analog has beneficial effects on hyperlipidemia and body weight (Gaich et al., 2013). Here, FGF21 is linked to obesity due to melanocortin 4 receptor deficiency.