Journal Article

Accuracy of body mass index in diagnosing obesity in the adult general population

Allison, T.G, Collazo-Clavell, M.L, Thomas, R.J, Lopez-Jimenez, F, Romero-Corral, A, Korinek, J, Sierra-Johnson, J, Batsis, J.A, Somers, V.K, Sert-Kuniyoshi, F.H

2008

Overview

Background: Body mass index (BMI) is the most widely used measure to diagnose obesity. However, the accuracy of BMI in detecting excess body adiposity in the adult general population is largely unknown. Methods: A cross-sectional design of 13 601 subjects (age 20-79.9 years; 49% men) from the Third National Health and Nutrition Examination Survey. Bioelectrical impedance analysis was used to estimate body fat percent (BF% ). We assessed the diagnostic performance of BMI using the World Health Organization reference standard for obesity of BF% >25% in men and>35% in women. We tested the correlation between BMI and both BF% and lean mass by sex and age groups adjusted for race. Results: BMI-defined obesity (30 kg m- 2) was present in 19.1% of men and 24.7% of women, while BF% -defined obesity was present in 43.9% of men and 52.3% of women. A BMI30 had a high specificity (men=95% , 95% confidence interval (CI), 94-96 and women=99% , 95% CI, 98-100), but a poor sensitivity (men=36% , 95% CI, 35-37 and women=49% , 95% CI, 48-50) to detect BF% -defined obesity. The diagnostic performance of BMI diminished as age increased. In men, BMI had a better correlation with lean mass than with BF% , while in women BMI correlated better with BF% than with lean mass. However, in the intermediate range of BMI (25-29.9 kg m- 2), BMI failed to discriminate between BF% and lean mass in both sexes. Conclusions: The accuracy of BMI in diagnosing obesity is limited, particularly for individuals in the intermediate BMI ranges, in men and in the elderly. A BMI cutoff of30 kg m- 2 has good specificity but misses more than half of people with excess fat. These results may help to explain the unexpected better survival in overweight/mild obese patients.

• Publisher: Nature Publishing Group UK,Nature Publishing,Nature Publishing Group
• Subject: Accuracy / Adipose tissues / Adult / adults / age / Aged / Aged, 80 and over / Analysis / bioelectrical impedance / Biological and medical sciences / Body Composition / Body Composition - physiology / Body fat / Body Mass Index / Clinical medicine / Cross-Sectional Studies / Diagnosis / diagnostic techniques / Electric Impedance / Epidemiology / Female / gender differences / Health Promotion and Disease Prevention / Humans / Impedance / Internal Medicine / lean body mass / Male / Measurement / Medical sciences / Medicine / Medicine & Public Health / men / Metabolic Diseases / Middle Aged / Mortality / Nutrition / Obesity / Obesity - diagnosis / Obesity - epidemiology / original-article / Overweight / physiology / Public Health / Sensitivity and Specificity / temporal variation / test sensitivity / test specificity / Weight control / women / Womens health / Young Adult