Based on the preceding discussion that PUFAs and their metabolites, hypothalamus and their peptides and neurotransmitters, BDNF, insulin receptors in the brain, gut peptides/hormones, cytokines, and gut microbiota play a role in obesity and DM, it is evident that all these factors/events are interrelated. This evidence concerns the gene BDNF and obesity due to melanocortin 4 receptor deficiency.