Body Composition in Coronary Heart Disease: How Does Body Mass Index Correlate With Body Fatness?

Background: Despite its many known shortcomings, body mass index (BMI) is the most widely used measure of obesity, in part because of its practicality. Other more physiologic measurements of obesity have been proposed, including percent body fat (BF). Few studies have compared BMI and BF, especially in patients with coronary heart disease (CHD). Methods: We studied 581 patients with CHD following major CHD events. We divided patients into low (<= 25% in men and <= 35% in women) and high BF (> 25% in men and. 35% in women) as determined by the sum of the skin-fold method and compared these findings with standard BMI determinations. Results: BMI and BF were highly correlated (r = 0.60; P < .001) and classified patients in the same category (obese vs nonobese) in 68% of cases. The agreement was optimal in the underweight (BMI < 18.5 kg/m(2)) and obese class II category (BMI 35-39.9 kg/m(2)), in which 100% of patients were classified as nonobese and obese, respectively, by both BMI and BF categories. The performance was worst in patients with BMIs in the overweight or preobese range (25-29.9 kg/m(2)), in which 58% of patients would be classified as obese according to BF criteria. Conclusions: Although some CHD patients are classified differently by BMI and BF, especially within the overweight BMI group, in general BMI and BF are highly correlated, especially in the underweight and obese BMI groups. Prospective studies are needed to determine which index of obesity best predicts risk in primary and secondary prevention.