Project Summary/Abstract Early adulthood is a significant period of risk for the development of obesity and excessive weight gain. Gender and race disparities in the prevalence of obesity become apparent in the transition between adolescence and adulthood, with young adult African American women exhibiting the highest prevalence of obesity. As behaviors established during young adult years are likely to persist in adulthood and because African American women have the highest prevalence of obesity and are at highest risk for weight gain during this time, young adulthood is a prime intervention target for establishing healthy behaviors related to weight management and preventing weight gain within this population. Social influences are an important factor in weight management behaviors. The social undermining of weight management behaviors can be defined as social interactions or events that threaten goal attainment of weight management behaviors (i.e., certain eating behaviors or physical activity), whether intentional or not. Social undermining is prevalent and may be more prevalent among young adults due to a heightened involvement in a variety of social environments and groups. Social undermining is an important intervention target as it may lead to dietary and exercise lapses, which may create energy imbalances and contribute to weight gain. However, social undermining remains under- addressed in weight management interventions. The characteristics of undermining may differ across communities, and African American women may experience different types of undermining or respond differently to undermining due to various cultural factors (e.g., body image, high cultural value of traditional foods). However, few studies have examined the experience or effects of undermining behaviors in African American women. The combination of this evidence suggests that there is a need to better understand the characteristics of social undermining related to weight management behaviors in young adult African American women who are trying to lose or maintain weight. Doing so will be a necessary first step for designing strategies for responding to social undermining in future weight loss or weight gain prevention interventions. Thus, the currently proposed study seeks to characterize the experience of and response to social undermining among African American young women, including examining associations with dietary and physical activity lapses, using a mixed-method approach combining ecological momentary assessment (EMA) methods with individual qualitative interviews.