Assessment of change in body fat percentage with DXA and eight-electrode BIA in centrally obese women

NEOVIUS, M., J. UDDEN, and E. HEMMINGSSON. Assessment of Change in Body Fat Percentage with DXA and Eight-Electrode BIA in Centrally Obese Women. Med. Sci. Sports Exerc., Vol. 39, No. 12, pp. 2199-2203, 2007. Purpose: To compare estimates of change in percent body fat (Delta%BF) between DXA and BlAg in abdominally obese women. Methods: Six-month longitudinal study of 106 women (baseline: age 48.2 +/- 7.6 yr; BMI 30.4 +/- 2.9 kg.m(-2); %BFDXA 45.8 +/- 3.6%) participating in an exercise-oriented behavior-change program (walking and bicycling). Fatness was measured by DXA and Tanita BC-418 (BIA(8)). Agreement between methods was assessed, and regression analysis was used to find predictors of the deviation between methods for estimating changes in fat mass percentage. Results: The methods differed significantly, both at baseline and follow-up (-5.0 and -4.4%BF, respectively; both P < 0.001). The mean Delta%BF was -1.1 +/- 2.5%BFDXA and -0.5 +/- 2.2%BFBIA8 (mean difference between methods 0.6 +/- 1.8%BF; P < 0.00 1; 95% limits of agreement -3.0 to 4.2%BF), with a range of -14.8 to 3.3%BFDXA and -9.4 to 3.5%BFBIA8. Approximately 49% of the variation in the difference between methods was explained by variations in age (beta = -0.05; P = 0.006), Delta BMI (beta = 0.98; P < 0.001), and Delta%BFDXA (P = -0.71; P < 0.001), indicating that the larger the change, the greater the discrepancy between methods. Conclusion: The difference between methods regarding Delta%BF was statistically significant, but it was of small magnitude. However, with increasing Delta%BF, increasing discrepancies were observed, implying that the BIA equipment may have limited validity for detecting larger fat losses. Both clinicians and researchers may benefit from awareness of this potential limitation.