Submitted to: American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/27/2001
Publication Date: 8/20/2002
Citation: WONG, W.W., HERGENROEDER, A.C., STUFF, J., BUTTE, N.F., SMITH, O.E., ELLIS, K.J. EVALUATING BODY FAT IN GIRLS: ADVANTAGES AND DISADVANTAGES OF DUAL-ENERGY X-RAY ABSORPTIOMETRY. AMERICAN JOURNAL OF CLINICAL NUTRITION. 2002. v. 76(2). p. 384-389. Interpretive Summary: Since the development of dual-energy x-ray absorptiometry (DXA) in the early 1990s, DXA has become widely accepted as a quick and easy way of measuring human body composition. However, no one has evaluated DXA's effectiveness in measuring the body fat of female adolescents, a group that has been shown to have a worsening problem with excessive weight gain, especially in African-Americans and Hispanics. It is important for doctors to accurately determine what part of the excess weight in a patient is fat or muscle. We evaluated the body composition of a total of 141 white, black, Asian and Hispanic girls between 9 and 17 years of age, comparing the results using DXA against the definitive four-compartment model that involves measurements of body water, bone mineral content and body density. Our results showed that in measuring a girl's body fat, the DXA numbers could be off by as much as 28 percent, even though DXA was relatively effective in estimating the body composition of the group as a whole, in comparison with the 4 compartment model. Therefore, we suggest that it would not be optimal to use DXA to measure the body fat of an individual adolescent girl, but it would be appropriate to use DXA to measure the body composition of a large and diverse group of adolescent girls. This information will be helpful to clinicians and researchers tracking overweight populations and evaluating individual cases of excess weight.
Technical Abstract: Dual-energy x-ray absorptiometry (DXA) has become one of the most widely accepted methods of measuring human body composition. However, DXA has not been evaluated in comparison with a criterion method in girls, despite continuing increases in excessive weight gain. To determine the bias and agreement between DXA and a 4-compartment (4-C) model in predicting the percent of fat mass (%FM) and percent of fat-free mass (%FFM) in a multiethnic group of girls. The %FM and %FFM of 73 White, 43 Black, 14 Hispanic, and 11 Asian girls aged 13.0 +/- 1.9 y measured by DXA were compared to the 4-C values which were based on measurements of body density, body water, and bone mineral content. The %FM and %FFM measured by the 2 methods were correlated at r=0.90 with a SEE of 3.3%; Bland-Altman analysis indicated an average bias of 3.9%. After nullification of the average bias, an individual estimate of %FM and %FFM by DXA could be under- or overestimated by 6.7%. DXA is an appropriate method for estimating body composition in a group of girls because its bias and limits of agreement were independent of age, ethnicity, and body fatness. However, the limits of agreement of 6.7% could translate into an under- or overestimation of an individual FM by 28% and FFM by 9% relative to the 4-C model. Therefore, DXA is not an optimal method of measuring the body fat of an individual girl.