Overweight and Obesity BMI Cut‐offs and Their Relation to Metabolic Disorders in Koreans/Asians

BMI (measured in kilograms per meters squared) is a commonly used measure of body fat. Global cut-off points for overweight (BMI = 25.0 kg/m2) and obesity (BMI = 30.0 kg/m2) have been set by the World Health Organization (WHO)1 (1). Since 1999, much debate has surrounded the appropriateness of these cut-off points in Asian populations. Several studies conducted in China (2, 3), Japan (4), Taiwan (5), and Hong Kong (6) have reported an association between a BMI >22.3 kg/m2 and increased atherogenic risk factors. In this issue of Obesity Research, Kim et al. (7) add to this literature using data collected in the 1998 Korea Health and Nutrition Examination Survey and report that the prevalence of diabetes, hypertension, and dyslipidemia has doubled at a BMI of 23.0 to 24.0 kg/m2 and tripled at a BMI of 26.0 kg/m2 in the Korean adult population. The authors propose that body fat and fat distribution at a BMI of 23.0 kg/m2 in Asians may be similar to those in whites at a BMI of 25.0 kg/m2. To promote healthy lifestyles and weight control, the WHO, the International Obesity Task Force, and the International Association for the Study of Obesity have proposed lower cut-off points for overweight (BMI = 23.0 kg/m2) and obesity (BMI = 25.0 kg/m2) in Asian and Pacific Island populations (8). There is disagreement, however, on the need to do so. Stevens has argued that few credible published data exist in support of elevated risk at BMI levels <25.0 kg/m2 in Asian populations (9, 10). An important issue in this debate concerns the use of BMI to define overweight and obesity across populations. The body composition profile in Asian populations differs from that in white and African-American populations. At the same BMI (11, 12, 13, 14), Asians have a higher percentage of body fat and more visceral adipose tissue compared with whites and African Americans; how then, can BMI be a suitable index for metabolic risk across races/ethnicities? Nonobese Asian-American women, for example, have a higher volume of visceral adipose tissue, adjusted for total adiposity, than white women (13). The relative risk of death by coronary heart disease is 8-fold higher in women with central adiposity (15). Distribution of adipose tissue as an independent predictor of an altered metabolic profile and cardiovascular disease (16) was originally identified from abdominal or waist circumference measures. A 1998 WHO recommendation of a waist circumference ≤80 cm for Asian women (1) was substantially larger than the now-recommended level of ≤75 cm (8). By Western BMI standards, Asian populations are often considered nonobese; the presence of obesity-related risk factors, however, is significant. More research is needed concerning associations between the amount and distribution of body fat and cardiovascular and metabolic risk factors in different ethnic/race groups. Appropriate investigations must involve the measurement of actual fat and its distribution; only then might we more clearly understand whether, and/or how, a single index such as BMI can be used as a screening tool.