Healthcare and research within the context of weight management report persistent difficulties with engagement. The aim of the current study was to identify factors which help and hinder engagement in weight-loss interventions and associated research. Participants (N= 98) who were currently or had recently attempted to lose weight by a diversity of means (including ‘going it alone’) were recruited through an online platform. Participants were asked to complete an online questionnaire with closed and open-ended questions assessing the factors which helped and hindered their engagement. Inductive thematic analysis of open-ended responses generated three themes related to (1) properties of the intervention (e.g., goal setting tools and peer support), (2) personal factors (e.g., emotion and skill) and (3) situational factors (e.g., time). Our findings resonate with key components of behaviour change approaches such as the COM-B model and potentially support their use in the context of improving engagement with weight-loss interventions and associated research. Future studies should take inventive approaches to understanding barriers to engagement amongst very disengaged individuals.