INS and obesity due to melanocortin 4 receptor deficiency: Obesity (defined as BMI ≥28 kg/m2); Obesity-related metabolic disorders: increased visceral fat area (VFA), elevated plasma glucose after the oral glucose tolerance test (OGTT), insulin resistance (reduced Stumvoll insulin secretion index), increased free fatty acids (FFA), elevated γ-glutamyltransferase (γ-GT)