Obesity disproportionately impacts sexual minority women. Behavioral weight loss programs are the gold standard treatment for mild to moderate obesity. The investigators have developed an online behavioral weight loss program that is effective, low-cost, and highly scalable. However, existing research suggests that tailoring treatment to address 3 well-established weight loss barriers in sexual minority women will be critical for maximizing the relevance and efficacy of behavioral weight loss for this group. In the Preparation Phase of this K23, the investigators developed 3 novel treatment components targeting sexual minority women's weight loss barriers (i.e., minority stress, low social support, and negative body image), the investigators piloted the program among sexual minority women of higher weight, and the investigators conducted individual qualitative interviews to elicit feedback on the intervention's acceptability, cultural relevance, usability, and feasibility, and this feedback was used to refine the program. In the Optimization Phase of this K23 (the current phase), 88 women will receive 12 weeks of Rx Weight Loss and will be randomized to receive 0-3 tailored components in a full factorial design with 23 (8) distinct combinations of components. Novel components that increase mean weight loss (by ≥2%) or the proportion of women achieving clinically meaningful weight loss (by ≥10%) at 6 months will be retained in a finalized obesity treatment package that the investigators will evaluate in a future randomized controlled trial (RCT) (Evaluation Phase). The aims of this study are to: Aim 2A (Optimization): Use a factorial experiment to determine how 3 novel components impact mean weight loss and the proportion of women achieving a 5+% weight loss at 6 months. Aim 2B (Mediation): Clarify how tailored components impact weight loss by testing hypothesized mechanisms of action (i.e., coping with stress, perceived social support, weight and shape concerns). This project will tailor and optimize an evidence-based online behavioral obesity treatment to enhance weight loss outcomes in sexual minority women.