Apnea is the medical term for "stopping breathing. " Many obese people have difficulty breathing when they sleep. The fatty tissues in the pharynx and neck can compress the airway and block it. When this occurs, the body's carbon dioxide levels rise to uncomfortable and unsafe levels. This may cause you to wake up many times throughout the night. For this reason, patients with sleep apnea sleep very poorly, and wake up in the morning still feeling tired. They remain tired throughout the day, sometimes falling asleep in the middle of a conversation or while driving. Sleep apnea may be relieved by using a CPAP or BiPAP device at night. These are breathing assist devices that are worn over the face to help with breathing at night time. After weight loss surgery, sleep apnea usually gets much better. Most patients who needed to use CPAP or BiPAP machines before surgery are able to stop using them within several months after surgery.