LEPR and obesity due to melanocortin 4 receptor deficiency: There are many rodent models of obesity and diabetes, such as ob/ob mice and db/db mice, which are deficient in leptin and the leptin receptor, respectively, KK-Ay mice, which are obese and diabetic mice independent of insulin, and high-fat diet (HFD) induced obesity (DIO; diet-induced obesity) model mice.