Measuring free-living energy expenditure using direct calorimetry

描述（由申请人提供）：目前测量自由生活个体每日总能量消耗（TDEE）的方法受到成本、准确性和对特定活动缺乏敏感性的限制。测量TDEE的准确、可靠和低成本的方法不仅需要改善临床结果（例如体重管理），而且需要满足公共卫生研究目标。在人体中，EE与总热损失成正比，即传导、对流、辐射和蒸发热流的总和，而热损失的测量是直接量热法的基础。然而，不可能准确地测量自由生活的人类的所有形式的热流，特别是蒸发热损失，这可能是总产热的一个重要组成部分。最近开发的一种能够测量各种形式热流的热流计在概念验证试验和试点研究中显示出了希望，但其测量TDEE的准确性尚未经过彻底测试。此外，准确性如何受到服装、环境温度和肥胖等因素的影响还没有得到研究。拟议研究的目标是：a)通过确定服装、环境温度、年龄、性别和身体成分等因素对准确性的影响，改进基于总热流的TDEE测量；b)将此方法的准确性与DLW和整个房间间接量热法的标准测量结果进行比较；c)将其精度与测量热通量但不能直接测量蒸发成分的类似仪器进行比较。拟议的研究具有创新性，因为它将测试一种基于与EE成正比的生理信号（产热）的方法的准确性。除了准确测量TDEE外，识别和区分不同类型的体育活动也是体育活动相关研究的重要目标，但这方面的能力有限。因此，拟议研究的另一个目标是确定热通量变化的测量是否可以用于识别特定活动中的EE，以及区分上半身和下半身活动。拟议的研究将允许改进一种技术，这将对临床实践和研究产生重大影响。这种新方法可能会在测量自由生活的人的TDEE以及评估身体活动和相关的能量成本方面提供实质性的改进。

DESCRIPTION (provided by applicant): Current approaches to measuring total daily energy expenditure (TDEE) in free-living individuals are limited by cost, accuracy, and lack of sensitivity to specific activities. Accurate, reliable, and low cost approaches for measuring TDEE are needed not only to improve clinical outcomes (e.g. weight management), but also to meet public health research objectives. In humans, EE is proportional to total heat loss, which is the sum of conductive, convective, radiant and evaporative heat flows, and measurement of heat loss is the basis of direct calorimetry. However, it has not been possible to accurately measure all forms of heat flux in free-living humans, particularly evaporative heat loss, which can be a substantial component of total heat production. A recently developed heat flow gauge with the capacity to measure all forms of heat flux has shown promise in proof of concept trials and pilot studies, but its accuracy in measuring TDEE has not yet been thoroughly tested. Moreover, how accuracy is affected by factors such as clothing, ambient temperature, and adiposity has not been studied. The objectives of the proposed research are to a) refine the measurement of TDEE based on total heat flux by determining how factors such as clothing, ambient temperature, age, sex, and body composition influence accuracy; b) compare the accuracy of this approach against the criterion measurements of DLW and whole-room indirect calorimetry; and c) compare the accuracy against a similar instrument that measures heat flux, but is not capable of directly measuring the evaporative component. The proposed research is innovative because it will test the accuracy of an approach that is based on a physiological signal (heat production) which is directly proportional to EE. In addition to accurately measuring TDEE, identifying and distinguishing different types of physical activity is an important goal of physical activity related research, but the capacity to do so is limited. Thus, an additional goal of the proposed research is to determine if measurement of changes in heat flux can be used to identify EE in specific bouts of activity and to differentiate between upper body and lower body activity. The proposed studies will permit refinement of a technology that will have major impact in both clinical practice and research. This new approach will potentially provide substantive improvements in the measurement of TDEE in free-living humans and in the assessment of physical activity and the associated energy cost. PUBLIC HEALTH RELEVANCE: Although instruments such as pedometers and heart rate monitors are helpful for those who use exercise to maintain their weight, they do not actually measure calories expended, which is a critical piece of information necessary for sustained weight management. The purpose of this study is to determine the accuracy of a new device that measures calories burned based upon heat produced by the body. Since heat production is directly proportional to calories burned, this device has the potential to accurately measure energy expended in many different settings.