Optimizing a Digital Mindfulness-Based Intervention to Reduce Risk Factors for Disordered Eating: A Multiphase Optimization Strategy (MOST) Feasibility Trial.

OBJECTIVE: Mindfulness-based interventions (MBIs) show promise in reducing risk factors for disordered eating. Digital delivery offers scalable reach, but effects vary and engagement is generally suboptimal-potentially due to the length, complexity, and variation in content. Identifying the most effective and engaging components is necessary to streamline interventions. Guided by the multiphase optimization strategy (MOST), this study assessed the feasibility of a factorial trial to evaluate whether including emotion regulation (ER) and self-compassion (SC) enhances the effects of decentred awareness and acceptance (DA + A, observing thoughts and feelings as separate from the self) in a digital MBI. METHOD: A 2 × 2 factorial design tested four intervention conditions. Each included DA + A content, with or without added ER and/or SC. Participants (N = 92, M = 21.1 years, range = 18-32) were randomized and given 3-weeks' access. Feasibility outcomes included recruitment, retention, data analysis, engagement, and acceptability. Intervention outcomes-weight and shape concerns, negative affect, mindfulness, ER, and SC-were assessed at baseline, postintervention, and 1-month follow-up. RESULTS: Recruitment exceeded targets. Retention was acceptable (58% completed postintervention and 59% follow-up assessments). All planned analyses for the main trial were feasible. Engagement met preregistered criteria (77%-85% completed Module 1 across ER and SC conditions; mean of four modules). Acceptability was high (M = 4.28/5). Participants valued reminders and provided design suggestions. DISCUSSION: Findings support progression to a fully powered optimization trial. This study demonstrates that MOST can be embedded within a pilot study, providing a foundation to develop more effective, engaging, and scalable interventions.