Body composition assessment in overweight women: validation of air displacement plethysmography

Abstract

Purpose: The purpose of this study was to evaluate the validity and reliability of air displacement plethysmography (ADP) compared to a dual energy x-ray absorptiometry (DXA) criterion for body composition measurement in overweight and obese women (BMI ≥ 25·0 kg m(2) ).

Subjects/methods: Twenty-four overweight and obese women (Mean ± SD; Age: 36·6 ± 12·0 years; Height: 166·4 ± 5·8 cm; Weight: 86·5 ± 14·2 kg; Body Fat: 38·5 ± 3·7%; BMI: 31·3 ± 5·5 kg m(2) ) were tested after an 8-h fast. Fat mass (FM), fat-free mass (FFM) and percent body fat (%BF) were measured by ADP and compared to values determined by the DXA criterion. FFM from DXA was calculated as lean mass plus bone mineral content. A paired samples t-test was used to test for significant differences in the body composition variables between methods. A one-way ANOVA along with intraclass correlation coefficient (ICC), SEM,%SEM and MD was used to represent reliability.

Results: Validity data comparing ADP and DXA demonstrated no significant difference in FM (ADP-DXA FM = 0·99 kg; P = 0·113), FFM (0·98 kg; P = 0·115) and %BF (1·56%; P = 0·540). Reliability data for ADP between the first and second trials showed no significant difference in FM (P = 0·168; ICC = 0·994; SEM = 0·668), FFM (P = 0·058; ICC = 0·973; SEM = 0·892) or %BF (P = 0·121; ICC = 0·971; SEM = 0·813).

Conclusions: For overweight and obese women, ADP was found to be a valid measure of FM, FFM and %BF when compared with DXA. The reliability of ADP was supported for all body composition variables.

Keywords: dual energy x-ray absorptiometry; fat-free mass; percent body fat; sensitivity; sex.

Figure 1

(a) The Bland–Altman analysis for Fat mass (FM). The middle solid line represents the mean difference between FM (kg) from air displacement plethysmography (ADP) – FM (kg) from Dual energy x-ray absorptiometry (DXA) and the upper and lower dashed lines represent ± 2 SD from the mean. Bias between ADP and DXA was not observed for FM, as indicated by a non-significant P value (P = 0.113). (b) The Bland-Altman analysis for Fat-free mass (FFM). The middle solid line represents the mean difference between FFM (kg) from ADP – FFM (kg) from DXA and the upper and lower dashed lines represent ± 2 SD from the mean. A nonsignificant P value (P = 0.115) indicated no bias between ADP and DXA for FFM (kg). (c) The Bland-Altman analysis for percent body fat (%BF). The middle solid line represents the mean difference between %BF from ADP–%BF from DXA and the upper and lower dashed lines represent ± 2 SD from the mean. Bias between ADP and DXA was not observed for %BF, as indicated by a non-significant P value (P = 0.540).