Based on the analysis of fat distribution by CT scanning, we have proposed a classification of obesity--visceral fat obesity--in which fat accumulation is predominant in the intraabdominal cavity. This type of obesity is more frequently accompanied by disorders of glucose and lipid metabolism and also with hypertension than subcutaneous fat obesity. We also showed that visceral fat obesity was present in almost 90% of obese patients with ischemic heart disease. From clinical and basic experiments, aging imbalance of sex hormone, overintake of sucrose, and lack of physical exercise have been suggested to be major factors for visceral fat accumulation. Since intraabdominal fat (mesenteric and omentum fat) have been shown to have high activities of both lipogenesis and lipolysis, its accumulation induces high contents of free fatty acids, a product of lipolysis, in portal circulation which goes into the liver directly. Excess free fatty acid may cause the enhancement of lipid synthesis and gluconeogenesis as well as insulin resistance, resulting in hyperlipidemia, glucose intolerance, and hypertension and finally atherosclerosis.