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ARS Home » Plains Area » Houston, Texas » Children's Nutrition Research Center » Research » Publications at this Location » Publication #94412
Title: MONITORING CHILDHOOD OBESITY: ASSESSMENT OF THE WEIGHT/HEIGHT2 INDEX

Author
item Ellis, Kenneth
item Abrams, Steven
item Wong, William

Submitted to: American Journal of Epidemiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/18/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Obesity is a major health problem which is worsening nationally among children and adults. The most widely used marker for obesity is the body mass index (BMI), which is the ratio of body weight to the square of height. However, few studies have evaluated the accuracy of this marker, especially when classifying overweight or obese children in a multiethnic population. We theorized that an improvement could be achieved in classifying individuals' degree of fatness by taking ethnicity into consideration. We compared the BMI with a direct measure of adiposity, using dual-energy X-ray absorptiometry to find the percentage of fat (ratio of fat mass to body weight) in nearly 1,000 children of both sexes and three ethnic groups. Our hypothesis turned out to be true. The ability of BMI to accurately predict an individual's degree of fatness was poor, although it provides reasonably good numbers for a group. We found gender and ethnic differences in the range of values for body fatness over the entire age range of our study, from 3 to 18 years of age. Thus, ethnicity should be taken into consideration when assessing an individual's adiposity. This invaluable study provides crucial new information of great use to health professionals who must use the most accurate measures to obtain and provide factual assessments of obesity.

Technical Abstract: The body mass index (BMI), defined as weight/height2, is often used to monitor childhood obesity. We have compared the BMI of 979 children (438 white, 283 black, and 258 Hispanic), ages 3-18 years, with a direct measure of adiposity obtained using dual-energy X-ray absorptiometry. The relationships between %Fat (defined as 100 x fat/body weight) and BMI were statistically significant (r2=0.34-0.70, p<0.0005), gender-dependent (p<0.0005), but BMI was a poor predictor of adiposity for the individual child (SEE=4.7%-7.3%). Use of BMI to identify children who are 'at risk' or 'overweight' was improved when ethnicity was taken into consideration. On a population basis, BMI can provide a general description of the adiposity characteristics of a healthy pediatric population; however, a false confidence may arise if BMI alone is used to assess an individual child's degree of adiposity. It is advantageous to accurately identify, as searly as possible, those children who truly have excess adiposity, but thi should not be done at the risk of falsely labeling a significant number of healthy children as overweight or obese.