If you lose weight, you can not only reduce the severity of you obstructive sleep apnea (OSA), you may eliminate it altogether.
Now, not everyone with OSA is overweight. You can be quite skinny and have severe OSA. In those folks weight loss obviously won't do much good.
But obesity is the number one risk factor for OSA, and the majority of patients with OSA, about 70%, are too fat. Unfortunately being too fat is increasingly prevalent in our population, and so the prevalence of sleep apnea is increasing, as well as the prevalence of other dangerous and disabling diseases linked to obesity.
Fat in and around one's abdomen, chest and neck – so called central obesity - appears to be the culprit, especially fat deposits around the upper airway. Having fat hips or thighs may not meet current aesthetic standards, but it does not carry much risk for disturbed breathing during sleep. In most studies neck size was as good a predictor of OSA as the usual measure of weight adjusted for height, body mass index (BMI).
Even modest weight loss may help. In one large study a weight decrease of 10% eliminated mild sleep apnea. More substantial weight loss can significantly improve patients with moderate or even severe OSA. You should also realize that the opposite is true. Studies show that a small weight gain can make OSA significantly worse.
Treatment of obesity in general, and in patients with OSA in particular, is very difficult. In one large study only 11% of overweight patients with OSA were successfully treated by weight loss alone, and by the end of three years only 3% maintained the improvement. Diet and exercise have very limited success, although there is some evidence that exercise training alone can improve OSA. Appetite suppressants and other medication can be helpful but concern about side effects limits their use. A safe and effective pill to decrease appetite is badly needed. Finally weight loss surgery, so called bariatric surgery, can be very successful and is increasingly safe, and should be strongly considered in extremely obese patients who have failed more conservative treatment.
The bottom line is if you are overweight and have OSA, make every attempt to change your lifestyle to include eating less and exercising more. And whatever you do, don't gain more weight.