Energy Expenditure in Subjects Successful at Weight Loss Maintenance

描述(由申请人提供)： 虽然许多人可以实现短期减肥，但长期减肥对大多数人来说是一个挑战。长期减肥成功的人总是报告说有高水平的体力活动。这项建议的目标是了解如何以及为什么高水平的体力活动对长期减肥至关重要。这个项目利用了国家体重控制登记处(NWCR)，该登记处跟踪了6000多名在一年内减掉30磅体重的人。我们假设，高水平的体力活动弥补了总每日能量消耗(TDEE)的减少，这是减肥的预期结果，并允许NWCR受试者在与减肥前相似的TDEE水平上实现能量平衡。我们基于以下观察结果：1)卡路里限制对减肥有效，但作为长期减肥的唯一策略通常无效；2)高水平的体力活动始终与成功的减肥保持相关；3)高水平的体力活动可能会改善食物摄入量的调节。我们还假设，在减轻肥胖状态下，体力活动的作用是纠正代谢效率的增加(低于预期的RMR)。我们基于这样的观察假设：1)经常锻炼的成年人的RMR比久坐不动的同龄人更大；2)对啮齿动物的研究一直表明，在减轻肥胖状态下，代谢效率提高；以及3)对人类的研究显示出好坏参半的结果，但很少有研究控制习惯性的体力活动水平。具体目的是：1)比较长期减肥成功的NWCR受试者与非减重匹配和肥胖对照组的TDEE及其成分。我们假设NWCR受试者的TDEE高于体重匹配的对照组，与肥胖对照组相似。这表明，肥胖程度减轻的受试者在减肥后，正在进行体力活动，以达到或接近减肥前的能量平衡水平。我们将使用双标记水来测量TDEE和总每日活动产热(TDAT)，间接热量法来测量RMR和食物的热效应，以及最先进的体力活动监测系统来评估运动活动产热(EAT)和非运动活动产热(NEAT)。2)比较NWCR受试者和对照组在自由生活条件下和在实验施加的能量流动减少(限制体力活动与能量摄入的等量减少相匹配)期间的RMR。我们假设，在自由生活条件下，NWCR受试者的RMR将类似于对照组，但当活动控制在类似的低水平时，RMR将比对照组下降得更多。我们将通过允许GCRC受试者72小时卧床休息，并提供旨在在这种受限活动状态下实现能量平衡的饮食来减少体液流量。

DESCRIPTION (provided by applicant): While many individuals can achieve short term weight loss, long term weight loss maintenance is a challenge for most people. High levels of physical activity are consistently reported by those who succeed in long-term weight loss maintenance. The goal of this proposal is to understand how and why high levels of physical activity are critical for long term maintenance of weight loss. This project takes advantage of the National Weight Control Registry (NWCR), which follows over 6000 individuals who have maintained a weight loss of >30 pounds for >one year. We hypothesize that high levels of physical activity compensate for the reduction in total daily energy expenditure (TDEE) that is the expected result of weight loss, and allow NWCR subjects to achieve energy balance at levels of TDEE similar to pre-weight loss levels. We base this hypothesis on the observations that 1) caloric restriction is effective for weight loss, but usually ineffective as a sole strategy for long term weight loss maintenance; 2) high levels of physical activity are consistently associated with success in weight loss maintenance; and 3) high levels of physical activity may improve regulation of food intake. We also hypothesize that physical activity functions to correct an increase in metabolic efficiency (a lower than predicted RMR) in the reduced obese state. We base this hypothesis on observations that 1) RMR is greater in adults who perform regular exercise than their sedentary peers; 2) studies in rodents have consistently shown evidence of an increase in metabolic efficiency in the reduced obese state; and 3) studies in humans have shown mixed results, but few studies have controlled for habitual level of physical activity. The specific aims are: 1) To compare TDEE and its components in NWCR subjects successful at long term weight loss maintenance to non-reduced weight matched and obese controls. We hypothesize that TDEE in NWCR subjects is higher than weight matched controls and similar to obese controls. This would suggest reduced obese subjects are using physical activity to achieve energy balance at or near the same level after weight loss as before. We will use doubly labeled water to measure TDEE and total daily activity thermogenesis (TDAT), indirect calorimetry to measure RMR and thermic effect of food, and state of the art physical activity monitoring systems to assess exercise activity thermogenesis (EAT) and non- exercise activity thermogenesis (NEAT). 2) To compare RMR under free living conditions and during an experimentally imposed period of reduced energy flux (restricted physical activity matched by an equivalent reduction in energy intake) in NWCR subjects and controls. We hypothesize that RMR in NWCR subjects will be similar to controls under free living conditions, but will decrease more than controls when activity is controlled to similar low levels. We will achieve a reduction in flux by admitting subjects to the GCRC for 72 hours of bedrest, and providing a diet designed to achieve energy balance in this restricted activity state.