Divisions of Endocrinology, University of Toronto, Toronto, Ontario, Canada.
Cardiology, University of Toronto, Toronto, Ontario, Canada.
J Nutr. 2019 Jul 1;149(7):1288-1293. doi: 10.1093/jn/nxz063.
Body mass index measures excess weight for size, and does not differentiate between fat mass (FM) and fat-free mass (FFM). Bioelectrical impedance analysis (BIA) is most commonly used to assess FM and FFM as it is simple and inexpensive. Variables from BIA measurements are used in predictive equations to estimate FM and FFM. To date, these equations have not been validated for use in adolescents with severe obesity.
In a cohort of adolescents with severe obesity (SO), a BMI ≥ 120% of the 95th percentile, this study aimed to 1) derive a BIA predictive equation data from air displacement plethysmography (ADP) measurements; 2) reassess the equation in a second validation cohort; and 3) compare the accuracy of existing body composition equations.
Adolescents with SO were assessed using ADP and BIA. FM values derived from ADP measurements from the first cohort (n = 27) were used to develop a BIA predictive equation (i.e., Hamilton). A second cohort (n = 65) was used to cross-validate the new and 9 existing BIA predictive equations.
Ninety-two adolescents (15.8 ± 1.9 y; BMI: 46.1 ± 9.9 kg/m2) participated. Compared with measured FFM using ADP: 1) the Lazzer, Hamilton, Gray, and Kyle equations were without significant bias; 2) the Hamilton and Gray equations had the smallest absolute and relative differences; 3) the Kyle and Gray equations showed the strongest correlation; 4) the Hamilton equation most accurately predicted FFM within ± 5% of measured FFM; and 5) 8 out of 9 equations had similar root mean squared prediction error values (6.03-6.64 kg).
The Hamilton BIA equation developed in this study best predicted body composition values for groups of adolescents with severe obesity in a validation cohort.
体重指数（BMI）用于衡量体重超标程度，无法区分脂肪量（FM）和去脂体重（FFM）。生物电阻抗分析（BIA）是最常用于评估 FM 和 FFM 的方法，因为它简单且廉价。BIA 测量的变量用于预测方程来估计 FM 和 FFM。迄今为止，这些方程尚未在患有严重肥胖症的青少年中得到验证。
在患有严重肥胖症（SO）的青少年队列中（BMI≥120%的第 95 百分位），本研究旨在 1）从空气置换体积描记法（ADP）测量中得出 BIA 预测方程数据；2）在第二个验证队列中重新评估该方程；3）比较现有的身体成分方程的准确性。
使用 ADP 和 BIA 评估 SO 青少年。第一队列（n=27）的 ADP 测量得出的 FM 值用于开发 BIA 预测方程（即 Hamilton）。第二队列（n=65）用于交叉验证新的和 9 个现有的 BIA 预测方程。
共有 92 名青少年（15.8±1.9 岁；BMI：46.1±9.9 kg/m2）参与了研究。与使用 ADP 测量的 FFM 相比：1）Lazzer、Hamilton、Gray 和 Kyle 方程没有显著偏差；2）Hamilton 和 Gray 方程的绝对和相对差异最小；3）Kyle 和 Gray 方程相关性最强；4）Hamilton 方程最准确地预测了 FFM，在测量 FFM 的±5%范围内；5）9 个方程中的 8 个具有相似的均方根预测误差值（6.03-6.64 kg）。
在验证队列中，本研究中开发的 Hamilton BIA 方程最能预测患有严重肥胖症的青少年群体的身体成分值。
