For example, HFD feeding to FFAR2 KO mice shows improved oral glucose tolerance test (OGTT) and insulin sensitivity along with lower fat mass and increased lean mass compared to wild type (WT) mice [28,30,33], indicating that the deletion of FFAR2 protects HFD-induced obesity/T2D. This evidence concerns the gene INS and obesity due to melanocortin 4 receptor deficiency.