Snoring is a major symptom of obstructive sleep apnea (OSA). However, while most people who have sleep apnea snore, not all people who snore have sleep apnea.
Snoring occurs when the flow of air from the mouth or nose to the lungs is disturbed during sleep, usually by a blockage or narrowing in the nose, mouth, or throat (airway).
If you are overweight, you may have more tissue in your neck, which can press down on the airway at night and block some of the airflow. Although your breathing does not stop, your breaths may be smaller, so the oxygen levels in your blood may go down. You may snore loudly and sleep badly.
WebMD Medical Reference from Healthwise