Overview of the Metabolic Syndrome
Professor, Department of Medicine and Physiology, University of Toronto; Head, Division of Endocrinology and Metabolism, University Health Network and Mount Sinai Hospital; Canada Research Chair in Diabetes
Resistance to the normal physiological actions of insulin, with its many metabolic and health consequences, arises from a complex interplay between genetic predisposition and lifestyle factors, particularly excess caloric intake and reduced levels of physical activity. Approximately 25% of the North American adult population is insulin resistant and it is now also appearing in young adults and children. Obesity-associated insulin resistance is becoming a public health crisis of epidemic proportions in many developing countries.
Obesity is now recognized as a proinflammatory condition that leads to a complex interaction between inflammatory mediators, impaired insulin action and metabolic abnormalities. Dyslipidemia is a common consequence of insulin resistance and contributes significantly to the development of premature and aggressive atherosclerosis. Type 2 diabetes and other insulin-resistant states are commonly associated with hypertriglyceridemia, low levels of high-density lipoprotein (HDL) cholesterol and a predominance of atherogenic small, dense low-density lipoprotein (LDL) particles (but not necessarily elevated LDL-cholesterol) which, along with hypertension and waist adiposity are all components of the metabolic syndrome. Individuals with hypertension are at greater risk of cardiovascular disease when it occurs in conjunction with dyslipidemia.
Weight reduction in those who are overweight or obese and increased physical activity lead to reduced inflammation; improvement in insulin action, glycemic control (in those with diabetes) and blood pressure (in those who are hypertensive); reductions in lipoprotein production rates and the consequent improvement in the associated dyslipidemia and other deleterious consequences of the metabolic syndrome. A balanced diet consisting of whole foods rather than an extreme reduction in any particular macronutrient (e.g., low-fat or low-carbohydrate diets), portion control, and an increase in daily physical activity is strongly advised.
