Postpartum weight retention (PWR) is a significant contributor to obesity in women of reproductive age. PWR is associated with continued weight gain, obesity development later in life, and cardiovascular disease development (CVD). Among postpartum women, standard weight-loss interventions that address diet and physical activity have produced only modest effects. Prior interventions are limited by not adequately addressing poor sleep, a common issue in postpartum women. Despite epidemiological evidence on the relationship between sleep and obesity, standard weight-loss interventions rarely include key elements of sleep interventions. Integrating sleep interventions with diet and physical activity may enhance weight loss among postpartum women. The overall goal of this K01 is to develop and test the feasibility, acceptability, and preliminary efficacy of Sleep GOALS (Goal-focused Online Access to Lifestyle Support), an Internet-assisted multiple health behavior (diet, physical activity, and sleep) weight loss intervention for postpartum women. We will create Sleep GOALS by adapting and integrating an existing sleep intervention (TSC; Transdiagnostic Sleep and Circadian intervention) with a diet and physical activity weight-loss intervention (GOALS Lifestyles, an online version of the Diabetes Prevention Program). We will use intervention mapping to guide the 3-step adaptation process. First, we will conduct semi-structured interviews with a purposive sample of 12 primiparous women between 3 and 6 months postpartum with overweight or obesity to review the framework and content of TSC and GOALS Lifestyle to solicit their suggestions for adapting these interventions for postpartum women. Step 2: We will pre-test the intervention content by reviewing the proposed adaptations with the same participants. Step 3: We will use feedback from the participants and experts in behavioral sleep medicine, weight loss interventions, and behavior change to ensure the adaptations maintain the core elements of the original interventions and address the specific needs of postpartum women. (Aim 1). We will then randomize 40 postpartum women to Sleep GOALS or an education control group to test the feasibility, acceptability, and preliminary efficacy of Sleep GOALS (Aim 2). We will use the pilot trial results to inform the conduct of a larger and definitive randomized controlled trial. A multi-disciplinary team of experts will guide my training in 1) intervention development, to learn the science of behavioral change, frameworks for intervention development and adaptation, and principles of user-centered design; 2) behavioral sleep medicine, to learn to evaluate sleep problems and developing individual sleep management plans; and 3) randomized controlled trials to learn the best practices of conducting clinical trials research. Consistent with the NHLBI’s Strategic Goals and Objectives, this training will allow me to become an independent researcher who develops/adapts be...