Development of a stress- and acceptance-based weight gain prevention intervention using the Multiphase Optimization Strategy - Overweight and obesity impacts 82% of Black women. Existing behavioral weight loss approaches have been developed largely with White women, and produce modest weight losses often below clinically meaningful thresholds in Black women, which inadequately responds to weight disparities. For Black women, overweight and class 1 obesity have a weaker association with mortality, cardiovascular disease and type 2 diabetes compared to White women, suggesting that weight stability may be a clinically meaningful target. Preventing weight gain, as opposed to weight loss, aligns with Black women’s sociocultural values for higher body weight and shifts focus away from thinness, which may facilitate treatment uptake. Yet, weight gain prevention (WGP) interventions have largely been conducted in White, female, normal to overweight, young adult samples. Little WGP research has been conducted among Black women, and no WGP interventions address stress, known to impair diet and physical activity behaviors. K01 objective: To develop and test a novel stress- and acceptance-based WGP intervention for Black women that is relevant, acceptable, efficient and effective. Aim 1a: To examine the relationship between physical activity, psychosocial, and environmental variables among Shape participants at 12-months post-baseline. Aim 1b: To examine the relationship between weight change, psychosocial and environmental variables among Shape participants at 12-months post-baseline. Aim 2: To examine, refine, and test stress management and acceptance-based behavioral treatment components for WGP among Black women (n=60). Aim 3: To examine participants’ experience with stress and acceptance-based intervention components, stress, and the relationship to weight related behaviors in Black women (n=60). These aims coordinate with 4 training goals: (1) Develop expertise in the multiphase optimization strategy (MOST) and advanced intervention designs for application to weight control interventions with Black women to conduct preparation phase research in advance of an optimization study, (2) Develop methodological expertise in qualitative and mixed methods to explicate contexts that influence weight control behaviors in Black women, (3) Develop expertise in stress reduction, acceptance-based behavioral treatment, and WGP approaches to deliver a novel stress- and acceptance-based WGP treatment to an under researched population, (4) Develop grantsmanship skills to prepare a R01 as Principal Investigator to support an optimization study for weight gain prevention. Long-term objective: To become independent and strong in multiple methods, specializing in optimized behavioral weight control interventions applying the multiphase optimization strategy (MOST).