Interdevice variability in percent fat estimates using the BOD POD

Objective: To evaluate interdevice reliability in body density (Db) and percent body fat (% BF) using air-displacement plethysmography, the BOD POD ( BP) body composition system. Design and Setting: Duplicate body composition tests were performed in immediate succession on 50 adults (26 M, 24F; 21 - 53 y) using two BP units located in the same body composition laboratory. Results: Mean Db and % BF between BP1 and BP2 did not differ significantly for men (Delta Db = 0.0003 +/- 0.0008 g/ml, P = 0.632; Delta% BF 0.1 +/- 1.3, P = 0.665), while for women, there were small but significant differences in Db and % BF between BP1 and BP2 (Delta Db 0.0018 +/- 0.0003 g/ml, P = 0.001; Delta% BF 0.8 +/- 1.1, P = 0.001). The regression between % BF by BP1 and BP2 did not deviate significantly from the line of identity for both men and women (R-2 = 0.95, standard error of estimate (s. e. e.) = 1.23 % BF for men; R-2 = 0.97, s. e. e = 1.13 % BF for women). Individual variations in % BF estimates between the two BP units were within acceptable ranges (95% limits of agreement = -2.5 - 2.7 % BF for men; -1.4 - 3.0 % BF for women), and there was no trend in individual differences as % BF varied (r = -0.19, P = 0.359 for men; r = 0.09, P = 0.677 for women). Other subject characteristics, including age, body mass, height, and body mass index, did not significantly contribute to the differences in % BF estimates by the two BP units. Conclusions: No clinically significant differences in Db and % BF estimates exist between the BP units, and the interdevice variability of the BP has minimal impact on % BF estimates. Further, test-to-test reliability between BP units appears to be as good as within one unit.