Metabolic syndrome in the prevention of cardiovascular diseases and diabetes--still a matter of debate?

After metabolic syndrome was first introduced to identify persons at greater cardiovascular disease (CVD) risk, it has been associated with an increased risk of CVD and type 2 diabetes (T2D). Obesity has been considered as the fundamental factor in metabolic syndrome and it is thought to be mediated, at least in part by the role of the adipocyte in controlling circulating free fatty acids and the development of insulin resistance. However, the obese population is not perfectly overlapped with the population with metabolic syndrome. Is metabolic syndrome a better predictor than obesity to prevent CVD and T2D? Has metabolic syndrome been considered as a cluster of risk factors or an additional independent risk factor to assess CVD and T2D risk? The debate on the necessity of metabolic syndrome diagnosis seems not to be ended. Various definitions of metabolic syndrome were advocated by different organizations with emphasis on different components, and these definitions have different abilities to predict CVD and T2D among different populations because of fundamental philosophical differences. In the definitions of metabolic syndrome, only the cutoffs of each component were presented but rather continuous values or the degree of the severity of the syndrome with multiple cutoffs. Moreover, metabolic syndrome did not incorporate all the risk factors as known for CVD and T2D, such as physical activity. Future prospective studies with the measurement of sophisticated metabolic markers and of abdominal visceral and subcutaneous adiposity are needed to examine if the metabolic syndrome is a good CVD and T2D risk predictor over obesity and other risk factors. In practice, prevention action should be taken at the stage of obesity and providers need to pay attention to any components in the definition of metabolic syndrome even if the number of positive components has not achieved three or more.