Air displacement plethysmography for estimating body composition changes with weight loss in middle-aged Japanese men

Abstract

Aim: To examine the degree to which air displacement plethysmography (ADP) can track body composition changes in response to weight loss in obese Japanese men.

Method: 50 men, aged 30-65 years with a mean BMI of 30 kg/m(2), were included in a 3-month weight loss program. Percentage of fat mass (%FM) was determined by dual energy X-ray absorptiometry (DXA) and ADP at baseline and month 3.

Results: With 6.2 ± 4.3 kg of weight loss, %FM, as determined by DXA and ADP, significantly decreased by 3.9 ± 2.9% and 3.9 ± 3.3% respectively. There was no mean difference for change (Δ) in %FM between the two methods. DXA-derived Δ%FM significantly correlated with Δ%FM determined by ADP (R(2) = 0.48, p < 0.01). Furthermore, the Bland-Altman plots demonstrated no systematic bias for Δ%FM (r = -0.20, p = 0.17). However, %FM by ADP (r = 0.42) at baseline and Δ%FM by ADP (r = -0.54) were significantly correlated to the differences between Δ%FM by DXA and ADP.

Conclusion: These results suggest that ADP is comparably accurate for evaluating Δ%FM when compared with DXA, although there were proportional biases.

Fig. 1

Simple regression analysis for changes (Δ) in %FM determined by DXA and ADP. The bold solid line indicates the regression line between Δ%FM from DXA and ADP. The dashed lines represent 95% prediction intervals. ●: participants engaged in dietary program, ○: participants engaged in exercise program, SEE: standard error of estimate.

Fig. 2

Bland-Altman plots for the systematic bias in the estimation of changes (Δ) in %FM between DXA and ADP. The middle solid line indicates the mean difference between Δ%FM from DXA and ADP. The upper and lower dashed lines represent limits of agreement (± 2 SD from the mean). ●: participants engaged in dietary program, ○: participants engaged in exercise program.

Fig. 3

Relation of changes (Δ) in %FM determined with DXA minus the Δ%FM estimated by ADP to baseline %FM determined by ADP (left) and the Δ%FM determined by ADP (right). The middle solid line indicates the mean difference between Δ%FM estimated from DXA and ADP. The upper and lower dashed lines represent limits of agreement (± 2 SD from the mean). ●: participants engaged in dietary program, ○: participants engaged in exercise program.