The prevalence of obesity continues to be higher among Black adults compared to other racial/ethnic groups in the United States, contributing to multiple health disparities. Strong evidence suggests modest weight loss achieved through lifestyle behavior changes can reduce the burden of obesity-related conditions like diabetes, cardiovascular health, and some cancers, yet current standard behavioral weight loss interventions are not optimized for weight loss among Black adults. Cultural adaptation of these interventions is recommended to improve weight and weight-related outcomes. Specifically, familial social networks are considered an important obesity contextual factor to target for Black adults, providing opportunities for provision of social support, resources for coping with stressors, and positive interdependence in achieving joint goals. In the few studies incorporating family members in weight loss interventions targeting Black adults, While this limited research shows promise, the field of family-centered research in obesity has several areas in need of additional research, including identifying the most effective combination of family support and behavior change strategies. Our research team has previously developed and implemented family-centered behavioral weight loss interventions for Black adults, including both couples and family member dyads. weight loss outcomes are enhanced. In these studies, we observed clinically significant short-term weight loss and improvements in hemoglobin A1c; family interactions; dietary, physical activity, and diabetes self-care behaviors; session attendance; and self-monitoring behaviors. Building on these preliminary studies of multicomponent interventions, we propose applying two innovative methodologies to optimize a family-centered behavioral weight loss intervention for Black adults. First, using the engineering-inspired, Multiphase Optimization STrategy (MOST) and a highly efficient experimental design, we will identify which levels and combinations of 4 intervention components yield the greatest weight loss at 6 months. Black adults (n=256 dyads, 512 individuals--index participant with %0, 30 kg/m2; dyad partner with BMI 27.5 kg/m2) will receive a core behavioral weight loss intervention and be randomized to 4 additional components: 1) number of family skills sessions (10 vs. 5), 2) delivery mode (in-person vs. online), 3) family communication/conflict skills training (yes vs. no), and 4) family cohesion skills training (yes vs. no). Second, by augmenting the optimization trial with Social Network Analysis (SNA), we will identify the types of interactions dyad members have with their larger social networks (both family and non-family) and how these interactions influence their health and weight loss behaviors. Evidence generated will yield an optimized family- centered intervention for Black adults that can be fully evaluated in a subsequent randomized controlled trial.