Conversely, studies on genetic models of obesity and diabetes, such as those performed by Song et al. in ob/ob mice or by Okumura et al. in genetic KK-Ay mice (a diabetic strain developing type 2 diabetes with mild obesity, due to peripheral insulin insensitivity) [139], evidenced only antihyperglycemic effects, without changes in the obesity-related phenotype. Here, INS is linked to obesity due to melanocortin 4 receptor deficiency.