Effect of insulin resistance, dyslipidemia, and intra-abdominal adiposity on the development of cardiovascular disease and diabetes mellitus.

Abdominal obesity contributes to insulin resistance, a metabolic abnormality linked to the development of type 2 diabetes mellitus and cardiovascular disease (CVD). Insulin resistance generally precedes the development of type 2 diabetes. Currently, an estimated 10 million US adults have diabetes and another 25 million have impaired glucose tolerance (IGT), an intermediate step between insulin resistance and diabetes. The pathophysiologic mechanisms known to increase CVD risk in individuals with insulin resistance include formation of advanced glycation end products, hypertension, proinflammatory and prothrombotic states, and dyslipidemia (i.e., low levels of high-density lipoprotein cholesterol, increased levels of triglycerides, small, dense low-density lipoprotein cholesterol particles, apoplipoprotein B, and inflammation). The increased flux of free fatty acids from adipose tissue to the liver promotes dyslipidemia. Insulin resistance and impaired glucose tolerance are associated with increased CVD risk. Individuals with coexisting metabolic syndrome and diabetes have the highest prevalence rates of CVD. The Nurses' Health Study showed that CVD risk was elevated even before the development of diabetes compared with women who never developed diabetes. Lifestyle modification is recommended as the first-line treatment for obesity and its metabolic sequelae. Pharmacotherapy may be useful in patients for whom nonpharmacologic approaches alone are ineffective or insufficient. Primary care physicians play a critical role in the early identification and treatment of patients at increased risk for the development of type 2 diabetes and CVD because of their obesity and associated complications.