Obesity exacerbates OSA via several mechanisms; (1) neck adiposity decreases the size of the upper airway lumen, (2) abdominal adiposity decreases lung volumes and chest wall compliance, and increases airway resistance, (3) obesity-associated leptin resistance decreases ventilatory drive and response to hypercapnia [128,129]. The gene discussed is LEP; the disease is obesity due to melanocortin 4 receptor deficiency.