Visceral fat in relation to health: is it a major culprit or simply an innocent bystander?

The aim of this review is to look critically at the widely accepted notion that visceral fat accumulation is the main determinant of obesity related diseases. Most of the epidemiological evidence is based on anthropometric indicators of fatness and fat distribution and their implications for visceral fat accumulation may not be unequivocal. In most cross-sectional studies in which visceral fat is associated with the level of risk factors or presence of disease, no adjustment is made for potential confounders. There are potential confounders at different levels of the causal chains linking visceral fat to health. Firstly, there are aspects of body composition or fat depots associated with visceral fat accumulation such as total body fat or total subcutaneous fat. Total and subcutaneous fat are, by themselves, potentially strong determinants for metabolic disturbances and disease. Secondly, there are behavioural factors (for example smoking, alcohol consumption, physical activity, dietary habits) which have been found to be associated with both the amount of visceral fat and health outcomes. Thirdly, there are hormonal mechanisms (adrenal and gonadal steroids as well as growth hormone) which may affect both the accumulation of visceral fat as well as the development of diseases. Finally, even a associations between visceral fat and risk factors or presence of diseases would be firmly established, the causality of the observed associations may not always be easy to interpret. Prospective studies are needed with appropriate control of potential confounding variables. It is concluded that, based on the current evidence, it is difficult to quantify the independent contribution of visceral fat to the development of a variety of chronic diseases.