Article Summary Obesity, Metabolic Syndrome, and Cardiovascular Disease. Grundy SM. J Clin Endocrinol Metab. 2004;89:2595-2600. Objective: To assess the effects of obesity on increased risk for atherosclerotic cardiovascular disease (ASCVD) and metabolic syndrome. Observation: A substantial percentage of ASCVD is a result of obesity mediated by type 2 diabetes. Risk factors that predispose patients to ASCVD have been termed metabolic syndrome, or prediabetes. Other complications of obesity include the comorbidities of fatty liver, osteoarthritis, polycystic ovarian disease, hypercholesterolemia, and sleep apnea. Clinicians can diagnose obesity in patients by measuring body mass index (BMI) and waist circumference. In the US, obesity is defined as a waist circumference of >39.8 inches (102 cm) in men and >34.3 inches (88 cm) in women. The metabolic syndrome is a combination of risk factors that may include dyslipidemia, elevated blood pressure, high blood glucose levels, a prothrombotic state, and a proinflammatory state. Some of these risk factors are not measured as a normal part of clinical practice. The National Cholesterol Education Program Adult Treatment Panel III report proposed that a diagnosis of metabolic syndrome can be made if a patient has 3 of 5 features: increased waist circumference; triglycerides of >150 mg/dL; HDL <40 mg/dL in men or <50 mg/dL in women; blood pressure of >130/85 mm Hg or on hypertensive therapy; blood glucose levels of >100 mg/dL. Debate continues over the relationship of obesity and metabolic syndrome to insulin resistance, although studies show that most people who have multiple risk factors are insulin resistant. This observation has led to the concept that insulin resistance is a causative factor of the syndrome. Regardless of debate, it is understood that people with metabolic syndrome have a twofold increase in risk for cardiovascular disease compared with those without it. Conclusion: It is a recognized fact that cardiovascular disease and diabetes have serious implications for the long-term health of an aging population. The real challenge is how best to intervene at the public health level to reduce the increasing prevalence, risk factors, and cost of obesity in the US.