Assessment of Energy Intake in Free-Living Subjects Using Stable Isotopes

描述（由申请人提供）： 肥胖是一个能量平衡的问题。当能量消耗跟不上摄入量时，脂肪组织就会积累到过剩的水平。现代工具可用于监测能量方程的三个组成部分中的两个：身体成分和能量消耗。然而，能量摄入仍然通过标准的食物摄入自我报告问卷进行评估。基于卡路里的工具在提供饮食模式数据方面很有用，但可能不准确和有偏见，特别是对于可能低估其能量摄入的超重个体。拟议的探索性研究的目的是开发一种实用的工具，可以测量自由生活的成年人的平均能量摄入量。在这项建议中，我们提出的证据表明，简单的监测呼吸二氧化碳中的同位素清除率可以提供有关脂肪，蛋白质和碳水化合物摄入量的定量信息。我们的方法包括数学建模和临床验证。该数学模型将模拟C-13标记的脂肪酸的动力学，作为脂肪、蛋白质和碳水化合物摄入量、身体组成和能量消耗的函数。一剂C-13标记的脂肪酸之后，在呼吸中检测C-13数天。初步的计算机模拟模型表明，脂肪和蛋白质的摄入量对C-13消除曲线的形状有不同的和可预测的影响。同位素清除的详细动力学参数将通过实验测量。第二个实验将通过使用全身碳库模型和每餐给药来检验以下假设：给药C-13标记脂肪酸后呼吸中的C-13/C-12比率是总燃料摄入量的指数。这项研究的成果将是一个充分发展的稳定同位素为基础的工具，通过评估能量摄入服务于能量平衡研究。如果成功的话，它将成为能量摄入的双重标记的水是今天的能量消耗。

DESCRIPTION (provided by applicant): Obesity is a problem of energy balance. When energy expenditure does not keep up with intake, then adipose tissue accumulates to excess levels. Modern tools are available for monitoring two of the three components of the energy equation: body composition and energy expenditure. Energy intake, however, is still evaluated by standard self-report questionnaires on food intake. The questionnaire-based tools are useful in providing data on dietary patterns, but can be inaccurate and biased especially for overweight individuals who may underreport their energy intake. The purpose of the proposed exploratory research is to develop a practical tool that can measure average energy intake in free-living adults. In this proposal we present evidence that simple monitoring of isotope clearance in breath CO2 can provide quantitative information on fat, protein and carbohydrate intake. Our approach includes both mathematical modeling and clinical validation. The mathematical model will simulate the kinetics of C-13 labeled fatty acid as a function of fat, protein and carbohydrate intake, body composition, and energy expenditure. A dose of C-13 labeled fatty acid is followed by C-13 detection in breath for several days. Work with a preliminary computer simulation model indicates that fat and protein intake have different and predictable effects on the shape of the C-13 elimination curve. The detailed kinetic parameters of the isotope clearance will be measured experimentally. A second experiment will test the hypothesis that the C-13/C-12 ratio in breath after dosing with C-13 labeled fatty acid is an index of total fuel intake, by using a total body carbon pool model and dosing with every meal. The outcome of this research will be a fully developed stable-isotope based tool to serve energy balance studies by evaluating energy intake. If successful, it will become for energy intake what doubly labeled water is today for energy expenditure.