Peer Effects on Weight Loss and Other Health Behaviors

描述（由申请人提供）：了解青少年超重上升的原因和制定有效的公共卫生政策来扭转目前的上升趋势是至关重要的。青少年与体重有关的行为（如饮食和体育活动）经常受到同伴行为的影响。如果同龄人确实对青少年体重有影响，那么旨在减少青少年超重的政策可能会产生社会乘数效应，其中政策的总体影响大于个体参与者。我们的研究将首次评估同伴对青少年体重相关行为的影响，同时明确控制潜在的反向因果关系（互惠效应）和青少年对同伴的选择（选择）。考虑这些影响是很重要的，因为如果青少年行为和同伴行为之间的相关性不是因果关系，那么政策就不会导致社会乘数。拟议的研究将解决以下具体目标：目标1：确定同伴的体重影响青少年自身体重的机制。使用来自全国青少年健康纵向研究（Add Health）的数据，我们将检查同伴对以下青少年体重相关行为的影响：(a)体重自我认知，(b)身体（in）活动水平，(c)饮食模式，(d)体重管理活动。添加健康允许我们在多个级别定义同伴组，包括使用指定的友谊关系和年级级别。将使用几种经验策略来解决目标1，包括基于外生变量估计朋友选择的多阶段程序；另一种年级同辈的定义，在学校内不受选拔的影响；使用前两波添加健康值来控制反向因果关系的同伴变量滞后值；每所学校使用指标变量来控制学校层面的混杂（未观察到的）影响。我们将测试同伴影响的性别差异。目标1的结果将有助于政策制定者瞄准那些有可能从目标青少年向其同龄人产生最大溢出效应的行为。目的2：估计针对青少年超重的政策的隐含社会乘数。使用Aim 1的结果，我们将计算每个与权重相关的行为的社会乘数的大小。了解社会乘数的大小对于评估旨在改善青少年体重的公共卫生政策的有效性和成本效益至关重要。如果不考虑社会乘数，就会低估有效的公共卫生政策在减少青少年超重方面对人口水平的影响。

DESCRIPTION (provided by applicant): It is vitally important to understand the causes of the rise in adolescent overweight and to develop effective public health policies to reverse the current upward trend. Adolescent weight-related behavior (e.g., diet and physical activity) is often influenced by the behavior of peers. If peers do have an influence on adolescent weight, then policies aimed at reducing adolescent overweight could have social multiplier effects in which the impact of the policy is larger in the aggregate than for individual participants. Our study will be the first to estimate the influence of peers on adolescent weight-related behavior while explicitly controlling for potential reverse causation (reciprocal effects) and adolescents' choice of peers (selection). Accounting for these effects is important because if the correlation between adolescent behavior and peers' behavior is not causal, then policies would not lead to social multipliers. The proposed research will address the following specific aims: Aim 1: To identify the mechanisms through which peers' weight affects an adolescent's own weight. Using data from the National Longitudinal Study of Adolescent Health (Add Health), we will examine the influence of peers on the following adolescent weight-related behaviors: (a) self-perception of weight, (b) physical (in) activity levels, (c) eating patterns, and (d) weight management activities. Add Health allows us to define peer groups at several levels, including using nominated friendship relationships and grade level. Several empirical strategies will be used to address Aim 1, including a multistage procedure that estimates friend selection based on exogenous variables; an alternative definition of peers at the grade level, which within schools is not affected by selection; lagged value of peer variables using the first two waves of Add Health to control for reverse causation; and the use of indicator variables for each school to control for confounding (unobserved) influences at the school level. We will test for gender differences in the influence of peers. Results for Aim 1 will help policy makers target those behaviors that have the potential for the largest spillovers from targeted adolescents to their peers. Aim 2: To estimate the implied social multiplier for policies aimed at adolescent overweight. Using the results from Aim 1, we will calculate the size of social multipliers for each weight-related behavior. Understanding the magnitude of the social multiplier is crucial for assessing the effectiveness and cost-effectiveness of public health policies aimed at improving adolescent weight. Failure to account for social multipliers would undervalue the population-level impact of effective public health policies to reduce adolescent overweight. PUBLIC HEALTH RELEVANCE: If peers have an influence on adolescent weight, then policies aimed at reducing adolescent overweight could have social multiplier effects in which the impact of the policy is larger in the aggregate than for individual participants. The accurate estimates of social multipliers for adolescent weight-related behavior that will be provided by this research are crucial for evaluating the effectiveness of public health policies. Failure to account for social multipliers would undervalue the population-level impact of effective public health policies to reduce adolescent overweight.