Optimal Timing of Exercise Initiation Within a Lifestyle Weight Loss Program

描述（由申请人提供）：尽管生活方式干预对减肥有短期效果，但许多人在一年内体重反弹明显。有规律的体育活动（PA）是持续减肥的最佳预测指标之一，目前的活动指南建议高水平的PA以防止减肥后体重反弹。然而，在饮食和运动干预同时进行的典型减肥计划中，大多数人不能达到或维持高水平的PA。因此，有必要评估新的策略，以促进坚持高水平的PA生活方式减肥计划。在减肥计划中开始运动的最佳时机是一个以前没有研究过的领域。本提案的总体目标是评估在饮食引起的体重减轻之后（而不是同时开始）进行运动干预，在多大程度上提高了运动的坚持性，并促进了长期的体重减轻。减肥后开始运动可以提高运动的接受度和坚持度，并促进长期减肥，因为：1)在体重较低时运动可能更容易进行，2)减肥后损伤率（和运动损耗）可能会减少，3)一次专注于单一行为改变可能更有效（而不是试图同时改变饮食和运动行为）。基于这些原因，我们认为在饮食引起的最初减肥期后开始运动可能更有效。我们的总体假设是

DESCRIPTION (provided by applicant): Despite the short-term effectiveness of lifestyle interventions for weight loss, many individuals regain a significant amount of weight within a 1 year period. Regular physical activity (PA) is one of the best predictors of sustained weight loss and current activity guidelines recommend high levels of PA to prevent weight regain after weight loss. However, most individuals do not achieve or sustain high levels of PA during typical weight loss programs in which diet and exercise interventions are initiated concurrently. Thus it is essential to evaluate novel strategies to promote adherence to high levels of PA within a lifestyle weight loss program. The optimal timing of exercise initiation within a weight loss program is an area that has not previously been studied. The overall objective of this proposal is to evaluate the extent to which an exercise intervention timed after diet-induced weight loss (rather than initiated concurrently) improves exercise adherence and facilitates long-term weight loss. Exercise initiation after weight loss may improve exercise adoption and adherence and promote long- term weight loss because: 1) exercise may be easier to perform at a lower body weight, 2) injury rates (and exercise attrition) may be reduced after weight loss and 3) it may be more effective to focus on a single behavior change at a time (rather than attempting concurrent changes in diet and exercise behaviors). For these reasons, we believe it may be more effective to initiate exercise after an initial period of diet-induced weight loss. Our overall hypothesis is that sequential delivery of diet and exercise interventions will result in improved weight loss at 18 months when compared to a traditional program in which identical diet and exercise interventions are initiated simultaneously. The study design involves an 18 month randomized trial within which obese subjects receive either standard behavioral therapy (Standard BT) or sequential behavioral therapy (Sequential BT). Standard BT will receive a traditional behavioral weight loss program where diet and exercise changes are initiated simultaneously. Sequential BT will receive a program that focuses solely on dietary changes in the initial 6 months, and then incorporates exercise in the ensuing 6 months. Both groups will be followed for 18 months to assess long-term weight loss. In Aim 1 we will assess the effect of timing of exercise initiatio on weight loss and body composition. In Aim 2 we will assess the effect of timing of exercise initiation on free living PA and cardio-respiratory fitness. In Aim 3 we will assess the effect of timing of exercise initiation on adherence to dietary weight control behaviors. In Aim 4 we will explore mechanisms (perception of exercise, exercise related injuries, and behavioral constructs related to our hypothesis) through which timing of exercise initiation may impact long-term weight loss. The approach is innovative as it focuses on determining the optimal time to begin exercise rather than evaluating a specific frequency, intensity, or duration of exercise. The proposed study is significant as it could identify a strategy that could aid in the development of more effective obesity treatment programs and help more people achieve and sustain a weight loss.