Project Summary Eating more than required to maintain a healthy weight is a major contributor to obesity, a serious risk factor for type 2 diabetes. Emotional eating, a common type of overeating, is when eating is triggered by affective states and some literature suggests it may be a predictor of weight loss treatment failure. Emotional eating research has focused primarily on the impact of negative emotions, even defining emotional eating in this way, however some research suggests positive affect influences eating behavior too. Laboratory studies inducing positive emotions in lean adults and adults with obesity have shown increased caloric intake, whereas an observational study of dieters suggests that feeling calm, a positive emotion, might reduce dietary lapses. These seemingly divergent findings can be explained by looking at emotion through the circumplex model of affect which suggests that valence (positive and negative) and arousal (high and low) are important features of emotion that influence how emotion affects behavior. Although arousal has rarely been considered in the emotional eating literature, findings like those mentioned above suggest that understanding emotional eating may require looking at affect from this lens. A clearer understanding of how affect influences eating behavior may help to inform just-in-time adaptive behavioral interventions, targeting emotional eating interventions to when they are needed most, to address the impact of emotions on eating behavior and ultimately weight loss. In the proposed observational study, we will use ecological momentary assessment to investigate the relationship between emotional valence and arousal and dietary lapses. For two weeks, 30 participants with obesity will record their emotions, dietary temptations, lapses, and the perceived severity of their lapses. We will investigate the relationship between low and high arousal, negative and positive emotions and 1) dietary temptations, 2) dietary lapses, and 3) severity of lapses. We hypothesize that low arousal positive emotions will be related to a lower odds of temptation, lapse, and decreased lapse severity, and that high arousal emotions regardless of valence and low arousal negative emotions will be related to a higher odds of temptation, lapse, and increased lapse severity. This project will provide extensive training in the use of ecological momentary assessment, measurement of emotion and eating behavior, and methods for analyzing longitudinal data, and provide the basis for a program of research focused on identifying and intervening on affective determinants of eating behavior.