The effectiveness and usability of online, group-based interventions for people with severe obesity: a systematic review and meta-analysis.

Long wait times, limited resources, and a lack of local options mean that many people with severe obesity cannot access treatment. Face-to-face group-based interventions have been found effective and can treat multiple people simultaneously, but are limited by service capacity. Digital group interventions could reduce wait times, but research on their effectiveness is limited. This systematic review aimed to examine the literature about online group-based interventions for adults with severe obesity (BMI ≥ 35 kg/m²). The review followed the PRISMA and PICOS frameworks. MEDLINE, Embase, CINAHL, Web of Science, and Cochrane Central Register of Controlled Trials were searched. Two authors independently screened articles. Data extraction, analysis, and quality assessment (using RoB2 and MMAT) was shared between two authors. A meta-analysis was conducted on eligible studies; other results were descriptively analysed. 20 papers reporting on 15 studies were included. Most studies reported some evidence of weight loss, but evidence of weight-related behaviour change was mixed. A meta-analysis on four studies indicated that online, group-based interventions had a statistically significant impact on weight loss (p = 0.001; 95% CI -0.69 to -0.17) with a small-to-moderate effect size, compared to waitlist or standard care conditions. Online interventions were considered more convenient but lack of familiarity with the group or counsellor, accessibility issues, and time constraints hindered engagement. Technical support, incentives, and interactive forums to improve group cohesion could mitigate these barriers. The findings suggested that online, group-based interventions are feasible and potentially beneficial, but barriers such as internet accessibility, digital literacy, and unfamiliarity with group members need to be mitigated. Key recommendations to improve experience and impact include providing instructions and run-throughs, building group cohesion, and providing session and additional content throughout the intervention. Future studies should focus on the influence of specific intervention characteristics and investigate the effect of these interventions compared to face-to-face interventions. Registration: National Institute for Health Research, PROSPERO CRD42021227101; https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021227101 .