The prevalence of metabolic syndrome has been increased recently because of westernized dietary habits and low physical activity in Japan. Metabolic syndrome is diagnosed by the accumulation of dislipidemia, glucose intolerance and/or high blood pressure caused by visceral obesity. The dislipidemia in metabolic syndrome is characterized by the presence of high plasma triglyceride and low HDL-cholesterol, which are associated with increase in small dense LDL and remnant lipoproteins, highly atherogenic lipoproteins. Metabolic syndrome is also often associated with fatty liver, which may be led to non-alcoholic steatohepatitis (NASH). Reduction of body weight and increase in physical activities are highly recommended in overweight patients to inhibit the development of metabolic syndrome, the dislipidemia and NASH.