Obesity with normal insulin sensitivity was characterized by lower glucagon levels and similar levels of glucose, insulinemia, GLP-1, and GIP compared with normal weight, while obesity with insulin resistance was characterized by higher levels of glucose and insulinemia and similar levels of glucagon, GIP, and GLP-1 compared with normal weight. The gene discussed is GLP1R; the disease is obesity due to melanocortin 4 receptor deficiency.