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Title: Percentage body fat in children and adolescents: Does DXA agree with a four-compartment (4-C) reference model?

Author
item Ellis, Kenneth
item SHYPAILO, ROMAN - BAYLOR COLLEGE OF MED

Submitted to: International Journal of Body Composition Research
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2005
Publication Date: 9/7/2005
Citation: Ellis, K.J., Shypailo, R.J. 2005. Percentage body fat in children and adolescents: Does DXA agree with a four-compartment (4-C) reference model? [abstract]. International Journal of Body Composition Research. 3:108.

Interpretive Summary:

Technical Abstract: Overweight and obese children and adolescents often become obese adults. Hence, intervention strategies are being focused at reducing excess fat gain during childhood. Body fatness, defined at the ratio of body fat to body weight, expressed as a percentage (%Fat), is considered the best body composition index for assessing an individual. We have compared the %Fat estimates obtained using whole-body dual-energy x-ray absorptiometry (DXA) with a 4-compartment (4-C) reference model bases on body water obtained by deuterium dilution, protein derived from whole-body potassium, and bone mineral content from DXA. A total of 497 subjects (275 males), ages 4 to 19 years, from three ethnic groups were measured. Bland-Altman analysis, paired t-test, and analysis of variance (ANOVA) was used to compare %Fat estimates; assess effects of gender, age, ethnicity, weight, height, and body mass index; and determine the mean bias and limits of agreement. The %Fat values for the two methods were highly correlated (R2=0.82, SEE = 3.6%) and unaffected by gender or ethnicity. The mean +/-SD values for DXA (23.9% +/-10.2%) were significantly lower (p<0.0005) than for the 4-C model (27.0% +/- 9.2%), with a mean difference of 3.0%, and 95% limits of agreement from -4.5% to 10.7%. DXA overestimated body fatness at lower values. Although DXA scanners are available in many clinical centers, and are becoming of de facto reference for calibration of field methods, the differences we have found dampen our enthusiasm for recommending DXA for this application in pediatric populations. Furthermore, as newer pediatric software versions for body composition are released, their accuracy needs to be verified with an independent criterion or reference model.