Whilst much research highlights the positive side of social support, some studies have identified a more negative side, particularly in the context of weight management and metabolic and bariatric surgery (MBS). This multi-methods thesis aimed to explore the role of partner social support throughout the MBS journey via five empirical studies. Study 1 employed a qualitative design with semi-structured interviews examining MBS patients’ (N = 30) perceptions of their partner’s support. Whilst some patients perceived social support as a positive resource, others described more negative aspects of support which had undermined their MBS goals through acts of sabotage. Study 2 used secondary qualitative data from an MBS online support forum (thread replies N = 569) to explore MBS saboteurs. Findings identified forms of sabotage behaviours, along with motivations, consequences, and strategies to mitigate these behaviours. Study 3 utilised a quantitative cross-sectional design to measure and assess perceived feeder behaviour in line with Ogden et al.’s (2020) Feeder Questionnaire among MBS patients and the general population (N = 121). The final 27-item Perceived Feeder Questionnaire consisted of five motivational dimensions (manners, status, waste avoidance, offloading, and affection) and one behaviour factor. Manners and affection were the greatest predictors of perceived feeder behaviour. Study 4 employed semi-structured interviews to investigate the experiences of partners of MBS patients (N = 10).  Partners’ experiences of adjusting to a post-MBS relationship varied, with some reporting positive changes, while others faced challenges. Finally, Study 5 used a co-design methodology to develop and evaluate a theory-informed psychoeducational animated video intervention to support the partners of MBS patients (stakeholders N = 6; partners N = 4). Feedback was very positive. Overall, findings from this thesis shed light on the less explored negative aspects of social support in the context of MBS. This underscores the critical importance of educating the support networks of MBS patients early in the journey to minimise these negative influences and foster a more constructive support system.