Effectiveness of Internet‐Delivered Cognitive Behavioural Therapy (ICBT) in Improving Weight‐Loss and Psychosocial Well‐Being Among Adults With High BMI: A Systematic Review.

Aim: To examine the effectiveness of Internet-delivered Cognitive Behaviour Therapy (ICBT) in improving psychosocial well-being and promoting weight-loss in adults ≥ 18 years with BMI ≥ 25 kg/m2. Background: Global obesity engenders significant physical and psychosocial health consequences. Second-wave ICBT focused on restructuring negative thoughts and behaviours has been explored as a potential intervention for elevated BMI and mental health concerns, but its effectiveness remains to be fully established, making further evaluation essential. Methods and Data Sources: Eight databases were searched from inception to January 2025 for randomised controlled trials (RCTs), including participants ≥ 18 years with BMI ≥ 25 kg/m2 and second-wave ICBT evaluating BMI, weight, depression, eating behaviours, and self-esteem. This review followed PRISMA 2020. Study quality was assessed using the Cochrane Risk of Bias (ROB 2) and GRADE. Data were extracted using a modified Cochrane form. Random-effects meta-analysis calculated Standardised Mean Differences (SMD) with 95% confidence intervals, with subgroup analyses exploring heterogeneity. Results: Nine trials with 2278 participants were included. Significant improvements were seen in BMI, weight, and depressive symptoms while self-esteem effects were small and non-significant. Compared with passive controls, ICBT showed greater improvements in BMI and weight, whereas differences versus active control were smaller and inconsistent. Face-to-face CBT demonstrated superior outcomes for depression and self-esteem. Male-tailored interventions showed greater improvements. Shorter programmes yielded larger short-term weight loss, while longer programmes supported more sustained effects. Narrative synthesis indicated improvements in emotional and external eating, with increased mindful and restrictive eating behaviours. Conclusion: ICBT improved weight, BMI, and depressive symptoms, with limited evidence for self-esteem. Male-tailored interventions and longer programmes may enhance sustainable outcomes. Impact: Future ICBT programs should integrate strategies targeting sustainable weight loss and psychosocial well-being to support long-term outcomes. No Patient or Public Contribution: Patients or members of the public were not involved, as this study synthesised previously published data. Trial Registration: PROSPERO registration number: CRD42024497961. © 2026 John Wiley & Sons Ltd.