Although the definition of metabolic syndrome is various, but it is normally accepted as a state that insulin resistance or glucose intolerance combined with hypertension or hyperlipidemia or obesity. Metabolic syndrome is a worldwide health problem, and the treatment is modification of life style, weight loss and medication. However, in most of the patients metabolic syndrome is considered not curable disease. Recent studies have shown that some bariatric surgery offers not only control the overweight but also metabolic syndrome. The exact mechanism is still unknown but decreased gastric volume and intestinal bypass itself seemed to play an important role to improve metabolic syndrome over just decreased weight.