Obesity hypoventilation syndrome (OHS) is a condition that occurs in individuals with severe obesity, leading to inadequate breathing during sleep. This results in low oxygen levels and high carbon dioxide levels in the blood, which can cause daytime sleepiness, fatigue, and difficulty concentrating. People with OHS often experience obstructive sleep apnea, where their airway becomes blocked during sleep. Treatment typically involves weight loss, the use of continuous positive airway pressure (CPAP) devices, and lifestyle changes to improve breathing and overall health.