The entire world is becoming overweight. Most people are motivated to try to lose weight for cosmetic reasons. Weight loss can decrease health risk factors and possibly improve prognosis. Weight loss can be difficult in people who are trying to stop smoking, as they tend to gain weight. Many weight loss systems are available and are not inexpensive. Athletes who are obese and fit must lose weight after retirement or suffer the consequences related to risk factors. Bariatric surgery seems to be the best way for morbidly obese patients to lose weight, assuming that they adhere to principles of risk factor modulation. Weight-loss medications work in most patients who also comply with lifestyle changes, but these drugs have a number of side-effects.