As we have already mentioned, obesity is characterized by a state of chronic, low-grade inflammation that is responsible for the development of obesity-related complications, since increased levels of pro-inflammatory cytokines, such as C reactive protein, IL-6, and PAI-1, are associated with impaired insulin sensitivity and increased risk of T2DM and metabolic syndrome in humans [54,55,56]. This evidence concerns the gene INS and obesity due to melanocortin 4 receptor deficiency.