Pathophysiology and pathogenesis of visceral fat obesity.

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 intra-abdominal 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 almost 90% of obese patients with ischemic heart disease have visceral fat accumulation. 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 intra-abdominal fat (mesenteric and omentum fat) have been show to have high activities of both lipogenesis and lipolysis, its accumulation induces a high content 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.