Examination of mechanisms (E-MECHANIC) of exercise-induced weight compensation

描述（由申请人提供）：高体重与高血压、血脂异常、炎症、代谢综合征、中风和冠心病的风险增加有关。虽然运动通常被认为是减肥的重要工具，但大量研究表明：1)考虑到消耗的卡路里，没有饮食干预的运动训练的减肥效果远远低于预期，这在运动剂量较大（如每天60分钟）时最为明显；2)运动对减肥的反应是非常不同的。然而，大多数体重管理指南建议每天锻炼一小时或更长时间，以促进体重减轻和防止体重减轻后反弹。显然，我们有必要找出导致大多数人（但不是所有人）运动无法产生显著减肥效果的机制，因为更好地了解导致这一现象的机制对于制定应对策略至关重要。主要机制包括运动引起的能量摄入增加、静息代谢率降低（根据体重变化调整）和非运动活动水平降低。E-MECHANIC试验的目的是比较两种剂量的运动对能量摄入和体重的影响。运动剂量将反映当前的建议：1)一般健康（~800- 1000千卡/周）和2)减肥和维持减肥（~2000 - 2500千卡/周）。运动组将不提供饮食干预，研究还包括一个不运动的对照组。主要结果变量是能量摄入以及预期体重减轻和观察到的体重减轻之间的差异（Wt. Lossdif）。能量摄入将使用两种最先进的方法来测量：双标签水和基于实验室的食物摄入测试。能量摄入被选为主要结果变量和限制运动引起的体重减轻的最有可能的补偿机制，但代谢（根据身体成分变化调整的静息代谢率）和活动水平（不包括有组织的运动）的变化也将被评估为可能的补偿机制和次要结果变量。最后，为了指导对抗补偿的干预措施的发展，我们将对参与者进行行为表型分析，以确定那些通过增加能量摄入来补偿和不补偿的参与者的特征。这项研究的结果将为健康和减肥建议提供重要信息，并确定对抗限制运动引起的体重减轻的补偿机制的方法。

DESCRIPTION (provided by applicant): High body weight is associated with increased risk for hypertension, dyslipidemia, inflammation, metabolic syndrome, stroke, and coronary heart disease. While exercise is commonly cited as an important tool for weight reduction, numerous studies have demonstrated that: 1) exercise training without a dietary intervention results in far less weight loss than expected given the expended calories and this is most evident when the exercise dose is large (e 60 minutes per day), and 2) the weight loss response to exercise is very heterogeneous. Nevertheless, most weight management guidelines recommend an hour or more a day of exercise both for promoting weight loss and preventing weight regain after loss. There is clearly a need to identify the mechanisms responsible for the failure of exercise to produce substantial weight loss in most but not all individuals, as having a better understanding of the mechanisms responsible for this phenomenon is critical to developing strategies to counter it. The leading mechanisms include exercise-induced increases in energy intake, decreases in resting metabolic rate (adjusted for change in body mass), and decreases in non- exercise activity levels. The purpose of the E-MECHANIC Trial is to compare the effect of two doses of exercise on energy intake and body weight. The exercise doses will reflect current recommendations for: 1) general health (~800- 1000 kcal/week), and 2) weight loss and maintenance of weight loss (~2000 to 2500 kcal/week). The exercise groups will not be provided with a dietary intervention, and the study also includes a non-exercise control group. The primary outcome variables are energy intake and the discrepancy between expected weight loss and observed weight loss (Wt. Lossdif). Energy intake will be measured using two state-of-the-art methods: doubly labeled water and laboratory-based food intake tests. Energy intake was chosen as the primary outcome variable and the most likely compensatory mechanism that limits exercise-induced weight loss, but change in metabolism (resting metabolic rate adjusted for change in body composition) and activity levels (excluding structured exercise) will also be evaluated as possible compensatory mechanisms and secondary outcome variables. Lastly, in an effort to guide the development of interventions to combat compensation, we will behaviorally phenotype participants to characterize those who do and do not compensate by increasing energy intake. The results of the study will provide important information for health and weight loss recommendations, and identify ways to counter compensatory mechanisms that limit exercise-induced weight loss. PUBLIC HEALTH RELEVANCE: Excess body weight is a significant risk factor for cardiovascular disease. Exercise is recommended for weight reduction, yet exercise training without a dietary intervention results in far less weight loss than expected given the expended calories and this is most evident when the exercise dose is large (e 60 minutes per day). In addition, the weight loss response to exercise is very heterogeneous. There is a need to identify the mechanisms responsible for the failure of exercise to produce substantial weight loss in most but not all individuals, as having a better understanding of the mechanisms responsible for this phenomenon is critical to developing strategies to counter it. The purpose of the proposed research is to identify the mechanisms responsible for the failure of exercise to promote the expected amount of weight loss. Specifically, the study will determine if exercise results in increased energy intake, decreased resting metabolic rate (adjusted for change in body mass), and/or decreased non-exercise activity levels, which compensate for the energy deficit caused by exercise and limit weight loss. The results of the study will provide important information for weight loss recommendations and the development of interventions to combat compensation.