Evans E M, Saunders M J, Spano M A, Arngrimsson S A, Lewis R D, Cureton K J
Department of Exercise Science, The University of Georgia, Athens 30602, USA.
Med Sci Sports Exerc. 1999 Dec;31(12):1778-87. doi: 10.1097/00005768-199912000-00013.
The purpose of this study was to determine whether the density (D(FFM)) and composition of the fat-free mass (FFM) and the accuracy of estimates of body composition from body density (%Fat(d)) are affected by diet and exercise.
Twenty-nine obese women (body mass index (BMI) = 25.0-43.7 kg x m(-2) and %Fat(d) = 35.7-47.1%) were assigned to one of three groups: diet only (DO, N = 9); diet and aerobic exercise (DE, N = 9); or control (C, N = 11). Measures of body density by hydrostatic weighing, body water by deuterium dilution, and bone mineral by whole-body dual-energy x-ray absorptiometry, and estimates of body composition from body density and from a four-component model were obtained before and after a 16-wk diet and exercise intervention.
Mean (+/- SD) changes in body mass were -7.2 +/- 7.4, -3.9 +/- 3.3, and +1.2 +/- 2.8 kg for the DO, DE, and C, respectively. The density and composition of the FFM did not change significantly (P > 0.05) in any of the groups. Individual changes in D(FFM) (-0.011 to +0.011 g x mL(-1)), and differences between changes in %Fat estimated using a four-component model and %Fat(d) (-2.1 to +2.7% body mass) were not related to changes in body mass (r = -0.08). Individual changes in D(FFM) were most strongly related to changes in water fraction (r = -0.95) and protein fraction (r = +0.88), and were unrelated to changes in the mineral fraction (r = +0.04) of the FFM.
We conclude that in obese women, the density and composition of the FFM are unaltered and densitometry correctly assesses group mean changes in body composition with moderate weight loss induced by diet or diet and aerobic exercise. However, individual deviations in D(FFM) from the assumed value of 1.1 g x mL(-1) are substantial, and a multi-component model in which body water is measured is needed to accurately assess individual body composition changes resulting from diet and exercise.
本研究旨在确定无脂肪质量（FFM）的密度（D(FFM)）和组成，以及根据身体密度估算身体成分（%Fat(d)）的准确性是否受饮食和运动的影响。
29名肥胖女性（体重指数（BMI）=25.0 - 43.7 kg·m⁻²，%Fat(d)=35.7 - 47.1%）被分为三组之一：仅饮食组（DO，N = 9）；饮食加有氧运动组（DE，N = 9）；或对照组（C，N = 11）。在为期16周的饮食和运动干预前后，通过水下称重测量身体密度，通过氘稀释法测量身体水分，通过全身双能X线吸收法测量骨矿物质，并根据身体密度和四成分模型估算身体成分。
DO组、DE组和C组的体重平均（±标准差）变化分别为-7.2±7.4、-3.9±3.3和+1.2±2.8 kg。在任何一组中，FFM的密度和组成均无显著变化（P>0.05）。D(FFM)的个体变化（-0.011至+0.011 g·mL⁻¹），以及使用四成分模型估算的%Fat变化与%Fat(d)变化之间的差异（-2.1至+2.7%体重）与体重变化无关（r = -0.08）。D(FFM)的个体变化与水分比例变化（r = -0.95）和蛋白质比例变化（r = +0.88）相关性最强，与FFM的矿物质比例变化（r = +0.04）无关。
我们得出结论，在肥胖女性中，FFM的密度和组成未改变，密度测定法能够正确评估饮食或饮食加有氧运动导致适度体重减轻时身体成分的组平均变化。然而，D(FFM)与假设值1.1 g·mL⁻¹的个体偏差很大，需要一个测量身体水分的多成分模型来准确评估饮食和运动引起的个体身体成分变化。
