PROJECT SUMMARY Over 70% of U.S. adults are classifiable as overweight or obese, and weight stigma, defined as the negative attitudes, prejudice, and discrimination directed at heavier individuals, is highly prevalent. Our long-term goal is to understand and ultimately mitigate the negative behavioral effects of weight stigma that pose risk for obesity and cardiovascular disease. In order to achieve this goal, we must first gain a fundamental understanding of the causal processes of weight stigma and how it functions in people’s lives to promote obesity. Therefore, the focus of this basic experimental study in humans (BESH) is to use an experimental manipulation as a probe in order to gain a fundamental causal understanding of the obesogenic nature of weight stigma. Much of the available evidence tying weight stigma to poor health outcomes is observational, precluding conclusions regarding causality. The few existing experimental studies that can infer causality only assess immediate outcomes in artificial lab settings. Moreover, the literature has thus far focused on documenting the negative effects of weight stigma, without attending to resilience factors that could confer protection against them. Therefore, our overall objectives are to (1) test the central hypothesis that weight stigma causes decrements in health behaviors in everyday life using ecological momentary assessment (EMA) and actigraphy, and (2) identify resilience factors that could, in future work, be targeted in weight stigma interventions. The central hypothesis is based on existing literature and our 8 preliminary studies, which include a study of 2,000 participants census-matched to U.S. population demographics demonstrating associations between greater weight stigma and binge eating and sleep disturbance. Our focus on health behaviors is important because behaviors account for 40% of preventable deaths and are strongly protective against obesity and cardiovascular disease. Moreover, there is evidence that the COVID-19 pandemic is detrimentally impacting diet, exercise, and sleep. Using a true experimental design, we will therefore pursue the following aims that capitalize on our deep experience manipulating weight stigma in laboratory experiments and our demonstrated expertise in ecological momentary assessment and actigraphy studies. AIM 1: Test the causal effects of weight stigma on diet, physical activity, and sleep in everyday life—we will randomly assign participants to a weight stigma vs. control manipulation and measure changes health behaviors in their everyday lives (3-day diet as captured by EMA food diaries, objectively measured physical activity captured by 24-hour actigraphy, and sleep, captured objectively by overnight actigraphy and subjectively self-reported sleep measures). AIM 2: Identify resilience factors that confer protection against the causal effects of weight stigma—we will test moderators drawn from two sources of theory (identity/belongingness and ...