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。高水平的体力活动是那些长期减肥成功的人一贯报告的。这个建议的目的是了解如何以及为什么高水平的身体活动是长期维持减肥的关键。该项目利用了国家体重控制登记处（NWCR）的优势，该登记处跟踪了6000多名体重减轻>30磅>一年的人。我们假设，高水平的体力活动弥补了每日总能量消耗（TDEE）的减少，这是减肥的预期结果，并允许NWCR受试者在TDEE水平上达到能量平衡，与减肥前的水平相似。我们基于以下观察结果提出这一假设：1）热量限制对减肥有效，但作为长期减肥维持的唯一策略通常无效; 2）高水平的体力活动始终与减肥维持的成功相关; 3）高水平的体力活动可能改善食物摄入的调节。我们还假设，身体活动的功能，以纠正增加代谢效率（低于预测的RMR）在减少肥胖的状态。我们基于以下观察结果提出了这一假设：1）定期锻炼的成年人的RMR高于久坐不动的同龄人; 2）啮齿类动物的研究一直表明，在减少肥胖状态下，代谢效率增加; 3）人类研究显示了混合的结果，但很少有研究控制了习惯性的体力活动水平。具体目标是：1）将成功维持长期体重减轻的NWCR受试者中的TDEE及其组分与未减轻体重的匹配和肥胖对照进行比较。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。这将表明减少肥胖的受试者正在使用身体活动来实现与之前相同或接近相同水平的能量平衡。我们将使用双标记水来测量TDEE和每日总活动产热（TDAT），使用间接量热法来测量RMR和食物的热效应，使用最先进的身体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受试者和对照者在自由生活条件下以及在实验施加的能量通量降低期间（限制体力活动，能量摄入等效减少）的RMR。我们假设NWCR受试者的RMR在自由生活条件下与对照组相似，但当活动控制在相似的低水平时，RMR会比对照组下降更多。我们将通过让受试者进入GCRC卧床休息72小时，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通量。

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.