From studies on humans and model animals, it appears that the genes implicated in the monogenic type of obesity may also carry mutations that stand out from the polygenic background (LEP, PCSK1, LEPR, POMC, MC4R, SIM1, NTRK2, BDNF, SH2B1, MRAP2, KSR2, ADCY3). The gene discussed is BDNF; the disease is obesity due to melanocortin 4 receptor deficiency.