In the cases of HIV and HCV infections, the persistence of viral infections in obese patients was complicated by accompanied ART or IFN therapies, respectively [22,23,43,44,45,60]; however, evidence from another side suggests that persistent viral infection and perturbation of IFN signaling exacerbate obesity development. The gene discussed is IFNA1; the disease is obesity due to melanocortin 4 receptor deficiency.