INS and obesity due to melanocortin 4 receptor deficiency: The effect of intranasally administered insulin on the CNS and the metabolic homeostasis of our body has also been studied in a review conducted by Ott et al. in 2012, wherein impaired insulin signalling in the brain was attributed to the development of type 2 diabetes and obesity, in which peripheral and possibly CNS insulin resistance is the hallmark, and Alzheimer's Disease, which has also been associated with insulin resistance as a contributor to the cognitive decline accompanying it [16].