Institute of Human Nutrition and Food Science, Christian-Albrechts-University, Kiel, Germany.
Obesity (Silver Spring). 2012 Apr;20(4):701-7. doi: 10.1038/oby.2011.269. Epub 2011 Aug 25.
Balance methods reveal changes in body energy, nitrogen, macro- and micronutrients as well as fluid in response to different feeding regimens. Under metabolic ward conditions, where physical activity is restricted and activity and food intake are controlled, the errors of estimates of energy intake, energy expenditure, and energy losses are about 2, 4, and 2%, respectively. Balance techniques can be used to validate techniques of in vivo body composition analysis (BCA). This is necessary since immediate and transient changes in body composition in response to a change in diet adversely affect the validity of techniques by violating the assumptions underlying standard methods (i.e., a constant composition or hydration of lean mass). Using two compartment reference methods, like densitometry, dual X-ray absorptiometry (DXA) or deuterium dilution, changes in fat mass with caloric restriction and overfeeding can be measured with a minimal detectable change (MDC) of 1.0-2.0 kg. However, when compared against balance data, the validity of these techniques to measure short-term changes in body composition is poor. The noninvasive and rapid new quantitative magnetic resonance (QMR) technique has a high precision with a MDC of 0.18 kg of fat mass. The validity of QMR to assess short-term changes in fat mass is challenged by comparison to balance data. Today, techniques used for in vivo BCA should be related to steady state conditions only, while in the nonsteady state, the use of balance methods is recommended to assess short-term changes in body composition.
平衡法可揭示机体能量、氮、宏量和微量营养素以及液体对不同喂养方案的变化。在代谢病房条件下，体力活动受限，活动和食物摄入受到控制，能量摄入、能量消耗和能量损失的估计误差分别约为 2%、4%和 2%。平衡技术可用于验证体内成分分析（BCA）技术。这是必要的，因为饮食变化引起的机体成分的即时和短暂变化会通过违反标准方法的基本假设（即瘦组织的恒组成或恒水合）而对技术的有效性产生不利影响。使用双 compartment 参考方法，如密度测定法、双能 X 线吸收法（DXA）或氘稀释法，可测量热量限制和过度喂养时体脂质量的变化，其最小可检测变化（MDC）为 1.0-2.0 kg。然而，与平衡数据相比，这些技术测量短期机体成分变化的有效性较差。非侵入性和快速的新型定量磁共振（QMR）技术具有高精确度，体脂质量的 MDC 为 0.18 kg。与平衡数据相比，QMR 评估短期体脂质量变化的有效性受到挑战。如今，用于体内 BCA 的技术仅应与稳态条件相关，而在非稳态条件下，建议使用平衡方法评估短期机体成分变化。
