1. ¹School of Leisure and Sport, Leeds Metropolitan University, Leeds, UK
2. ²Centre for Bone and Body Composition Research, University of Leeds, Leeds, UK
3. ³Imaging Science Group, School of Healthcare Studies, University of Leeds, Leeds, UK

Correspondence: D Radley, Leeds Metropolitan University, School of Leisure and Sports Studies, Beckett Park Campus, Fairfax Hall, Leeds LS6 3QS, UK. E-mail: d.radley@lmu.ac.uk

^*Guarantor: D Radley.

^†Contributors: DR performed data collection, statistical analysis and contributed to writing the paper. PJG was the chief project coordinator and contributed to writing the paper. CBC assisted in the design of the study, critically reviewed all parts of the paper and assisted in interpretation of the results. SC assisted in statistical analysis, interpretation of the results and critically reviewed all parts of the paper. BO performed technical measurements and contributed to writing the paper. JGT assisted in the design of the study and critically reviewed all parts of the paper.

Received 6 June 2002; Revised 7 November 2002; Accepted 26 November 2002.

Abstract

Objective: To evaluate the accuracy of percentage body fat (%fat) estimates from air displacement plethysmography (ADP) against an increasingly recognised criterion method, dual-energy X-ray absorptiometry (DXA), in young adolescents.

Design: Cross-sectional evaluation.

Setting: Leeds General Infirmary, Centre for Bone and Body Composition Research, Leeds, UK.

Subjects: In all, 28 adolescents (12 males and 16 females), age (means.d.) 14.90.5 y, body mass index 21.22.9 kg/m² and body fat (DXA) 24.210.2% were assessed.

Results: ADP estimates of %fat were highly correlated with those of DXA in both male and female subjects (r=0.84–0.95, all P<0.001; s.e.e.=3.42–3.89%). Mean %fat estimated by ADP using the Siri (1961) equation (ADP_Siri) produced a nonsignificant overestimation in males (0.67%), and a nonsignificant underestimation in females (1.26%). Mean %fat estimated by ADP using the Lohman (1986) equations (ADP_Loh) produced a nonsignificant underestimation in males (0.90%) and a significant underestimation in females (3.29%; P<0.01). Agreement between ADP and DXA methods was examined using the total error (TE) and methods of Bland and Altman (1986). Males produced a smaller TE (ADP_Siri 3.28%; ADP_Loh 3.49%) than females (ADP_Siri 3.81%; ADP_Loh 4.98%). The 95% limits of agreement were relatively similar for all %fat estimates, ranging from 6.57 to 7.58%. Residual plot analyses, of the individual differences between ADP and DXA, revealed a significant bias associated with increased %fat (DXA), only in girls (P<0.01).

Conclusions: We conclude that ADP, at present, has unacceptably high limits of agreement compared to a criterion DXA measure. The ease of use, suitability for various populations and cost of ADP warrant further investigation of this method to establish biological variables that may influence the validity of body fat estimates.