OSA affects approximately 1 per cent of the adult male population and is more common among obese patients. The mechanism for the relationship between obesity and OSA may be mechanical obstruction or hypoxemia. Patients with obesity often have other medical problems that can exacerbate or complicate OSA. The physician should look for other problems such as diabetes, hypertension, and coronary disease while evaluating an obese patient with OSA. Weight loss is important either as a primary therapy or in conjunction with surgical treatment of OSA. Weight loss methods include behavior modification with diet, very low calorie diets with behavior modification, and bariatric surgery. In morbidly obese patients, more dramatic means such as bariatric surgery or very low calorie diets seem to be preferable because of the significant reduction in the length of time it takes for patients to lose weight. Because of a tendency for obese patients to regain weight, it is important to follow the patients long term to prevent the regaining of weight.