Eighteen trials (n=5700) were included in the review. Overall study quality was average. Three of the 18 studies met eight of the ten checklist requirements. Most studies conducted intention-to-treat analyses and measured outcomes appropriately. Quality concerns included lack of reporting for method of randomisation and allocation concealment.
Weight loss: There were no differences in weight loss between web-based programs and control or minimal intervention in three studies. Significant heterogeneity was observed for this outcome. Participants reported significantly greater weight loss in enhanced web-based programmes versus education-only web-programmes (WMD 2.24kg, 95% CI 1.27 to 3.21, p<0.00001; three trials). No significant heterogeneity was observed.
Subgroup analyses that investigated the addition of behavioural therapy did not show a significant difference between groups. The addition of counselling significantly increased weight loss (WMD 2.76kg, 95% CI 1.31 to 4.21, p=0.0002).
Weight loss maintenance: Participants in web-based programs gained significantly less weight compared to control or minimal intervention (WMD -0.30kg, 95% CI -0.34 to -0.26, p<0.00001; two trials). No significant heterogeneity was observed. There were no significant differences reported between web-based interventions and face-to-face interventions.
Subgroup analyses reported no differences between groups for both frequent and minimal intensity face-to-face interventions.