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，脂肪组织就会积聚到过剩的水平。现代工具可以用来监测能量方程式的三个组成部分中的两个：身体成分和能量消耗。然而，能量摄入量仍然是通过标准的食物摄入量自我报告问卷来评估的。基于问卷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，特别是对于可能少报能量摄入量的超重个人。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。在这项提案中，我们提出的证据表明，简单地监测呼气二氧化碳中的同位素清除可以提供有关脂肪、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。数学模型将模拟C-13标记脂肪酸作为脂肪、蛋白质和碳水化合物摄入量、身体组成和能量消耗的函数的动力学。一剂量的C-13标记的脂肪酸之后，呼吸中的C-13检测几天。使用一个初步的计算机模拟模型表明，脂肪和蛋白质摄入量对C-13消除曲线的形状有不同的和可预测的影响。将在实验上测量同位素清除的详细动力学参数。第二个实验将通过使用全身碳池模型和每顿饭的剂量来验证这样的假设，即在服用C-13标记脂肪酸后，呼气中的C-13/C-12比率是总燃料摄入量的一个指标。这项研究的结果将是一个完全开发的基于稳定同位素的工具，通过评估能量摄入来服务于能量平衡研究。如果成功，它将成为能量摄入的双重标签，就像今天水的能量消耗一样。

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.