FTO and obesity due to melanocortin 4 receptor deficiency: The most recognized in the general population susceptibility genes involve CDKAL1, TCF7L2, SLC30A8, and CDKN2B (coding for proteins regulating pancreatic islets function, cyclin-dependent kinases, and zinc transporters) with some candidates associated with obesity and insulin-resistance genetic traits (such as FTO, PPAR-γ, IRS1) [44].