Related information on this website: In the Slide Library section: ATP III: Nutritional Components of the TLC Diet ATP III: The Metabolic Syndrome In the Current Literature section: Mediterranean Diet, Traditional Risk Factors, and the Rate of Cardiovascular Complications After Myocardial Infarction: Final Report of the Lyon Diet Heart Study de Lorgeril M, Salen P, Martin J-L, Monjaud I, Delaye J, Mamelle N. Circulation. 1999;99:779-785. AHA Dietary Guidelines; Revision 2000: A Statement for Healthcare Professionals From the Nutrition Committee of the American Heart Association Krauss RM, Eckel RH, Howard B, et al. Circulation. 2000;102:2296-2311.

Excess weight has serious repercussions on a person's health—besides compromising his or her cardiovascular health, this excess weight increases the individual's risk for developing hypertension, type 2 diabetes, and several forms of cancer, among other disorders. Today, more than half (55%–61%) of the adults in the United States are overweight or obese.^1,2 By helping these patients to lose weight and improve their overall conditioning, physicians can promote a reduction in their risk for cardiovascular disease (CVD).

As defined by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) of the National Institutes of Health (NIH), overweight is excess body weight from muscle, bone, fat, and/or body water, compared with set standards. Obesity refers to an abnormally high proportion of body fat.²
    The relation between obesity and CVD is complex. Some studies indicate that it is an independent risk factor. However, other studies have found that the association is weakened by multivariate adjustment for the established risk factors of blood pressure (BP), TC, HDL-C, and diabetes. In either case—independent risk factor or a cause of abnormalities directly linked to CVD—obesity contributes to cardiovascular morbidity and mortality.³

Syndrome Increases CHD Risk
Abdominal obesity is an underlying cause of the metabolic syndrome, a cluster of disorders that work not merely additively, but synergistically, to increase the risk of developing CVD (see "The Metabolic Syndrome").⁴ This syndrome, which increases the risk for coronary heart disease (CHD) at any LDL-C level, is also associated with "emerging risk factors" (eg, prothrombotic/proinflammatory states) that are common in obese persons but are not usually detected in a routine clinical workup.^3,5 The Third Report of the Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (ATP III) identifies the metabolic syndrome as a potential secondary target of risk-reduction therapy. Patients with this syndrome require intensified treatment to reduce obesity, increase physical activity, and correct associated lipid and nonlipid risk factors.⁵

Definitions of Obesity, Overweight
Body mass index, or BMI, represents body weight relative to height, and correlates strongly with total body fat content in adults. It has become the new standard for defining overweight and obesity. According to the NIH and the Centers for Disease Control and Prevention (CDC), overweight is defined as a BMI of 25 to 29.9 kg/m², and obesity as a BMI of 30 kg/m² or greater.^6,7 BMI can be calculated by dividing weight in pounds by height in inches squared, and then multiplying the quotient by 703.⁷
    According to a new analysis of the National Health and Nutrition Examination Surveys (NHANES) III, BMI correlates positively with BP and TC values, and inversely with HDL-C.⁸ Compared with their normal-weight counterparts, men in the highest obesity category have more than twice the risk of hypertension, hypercholesterolemia, or both, and women in the highest obesity category have four times the risk.⁸ One study showed that, in young men (aged 15 to 34 years) who had died of non–CVD-related causes, BMI was positively associated with fatty streaks and raised atherosclerotic lesions in the right coronary artery (RCA) and with microscopic lesion-grade atherosclerosis and stenosis in the left anterior descending artery. The association between BMI and raised lesions in the RCA was greater in young men with central obesity—a finding consistent with most other reports.⁹

Childhood and Adolescent Obesity
Perhaps one of the most alarming facets of the condition is the toll obesity is taking on children. According to the NIDDK, the proportion of overweight US children and adolescents has more than doubled from the 1960s and 1970s to the period of 1988 to 1994: from 5% to 11%.^2,10 The CDC, using data from NHANES II (1976–1980), III (1988–1994), and as well as 1999 NHANES data, found similarly disturbing trends¹: The prevalence of overweight in both groups nearly doubled between NHANES II (5%–7%) and NHANES III (11%). By 1999, 13% of children aged 6 to 11 years and 14% of those aged 12 to 19 years were overweight. Children and adolescents of African-American or Latino background have relatively greater rates of obesity.¹¹ All of these overweight/obese youngsters are at increased risk for developing heart disease in adulthood unless early intervention is undertaken.

Diagnosis
The NIH Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults recommend that physicians use BMI to assess overweight and obesity and to monitor body-weight changes.⁷ Because some very muscular individuals may meet criteria for being overweight without being obese,² physicians are advised to check for another indicator of overweight or obesity: waist circumference or waist-to-hip ratio (WHR; waist circumference divided by hip circumference).⁷ This is because excess abdominal fat, as opposed to excess fat deposited on the hips and/or thighs, is an independent predictor of risk factors and disorders associated with obesity.⁶ One study showed that, in middle-aged men, abdominal obesity—more than overall obesity—was an independent risk factor for the development of CHD.¹²
    For persons with a BMI of 25 to 34.9 kg/m², a waist circumference of greater than 40 inches in men or greater than 35 inches in women is considered to increase the relative risk of developing obesity-related risk factors.⁷ (These values should be decreased in persons who are under 5 feet tall.¹³) A WHR of 1.0 or higher signifies added risk.¹³
    Obese individuals' CVD risk is exacerbated by presence of the following⁷:

	established CHD, other atherosclerotic disease, type 2 diabetes, sleep apnea
	cigarette smoking, hypertension, high LDL-C (>160 mg/dL), low HDL-C (<35 mg/dL), impaired fasting glucose (110–125 mg/dL), family history of premature CHD
	sedentary lifestyle
	serum TG exceeding 200 mg/dL