Important genes associated with monogenic obesity consist of leptin (LEP), leptin receptor (LEPR), proopiomelanocortin (POMC), prohormone convertase 1 (PCSK1), MC4R, single-minded homolog 1 (SIM1), brain-derived neurotrophic factor (BDNF), and its receptor NTRK2 (commonly referred to as TrkB) [17,18]. Here, SIM1 is linked to obesity due to melanocortin 4 receptor deficiency.