ESTIMATING BODY FAT PERCENTAGE: TESTING VALIDITY AND RELIABILITY OF BIA AND DXA AGAINST BODPOD

• Published in: Nutrition & dietetics Vol. 70; p. 10
• Main Authors: Kruger, R, Ingram, M, Walsh, D, Von Hurst, R, Conlon, C, Stonehouse, W
• Format: Journal Article
• Language: English
• Published: Deakin Wiley Subscription Services, Inc 01.09.2013
• Subjects: Adults; Body fat; Regression analysis; Reliability; Validity
• ISSN: 1446-6368; 1747-0080
• DOI: 10.1111/1747-0080.12065

Body fat percentage (BF%) is most accurately predicted using air displacement plethysmography (BodPod) (gold standard method). Dual-energy X-ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA) also predict BF%, but have not been validated against the BodPod in a large sample with a range of healthy adults. The aim was to assess the validity and reliability of BIA and DXA against BodPod in estimating BF% in healthy adults. BF% of 164 adults (18-70 y) was measured twice within 5 days using BodPod, DXA and BIA. Agreement between measurements was analysed using t-tests, effect size, linear regression models and method of triads. Reliability was assessed by comparing and correlating repeat measurements (t-test; Pearson correlations). BIA showed excellent relative agreement to the true value (... = 0.97 [0.96, 0.98]) and to Bodpod (... = 0.88), but absolute agreement was biased and the limits of agreement wide (-4.25 to 8.37%). BIA underestimated body fat with 2%, across all BF% values, not differing between men and women. DXA showed excellent relative agreement to the true value (... = 0.97 [0.96, 0.98]) and to Bodpod (... = 0.92), and good absolute agreement despite wide limits of agreement (-6.13 to 6.91%). DXA overestimated extreme low BF% (all men) and underestimated high BF% (all women). BodPod, BIA and DXA showed excellent reliability with repeat measurements differing by less than 0.2% with very small 95% CIs. On average, BodPod BF% can be predicted from BIA measurements by adding 2%. DXA compares well to BodPod except at extreme BF% levels. (ProQuest: ... denotes formulae/symbols omitted.)