Eighteen RCTs (n=1,636) were included in the review. Sample size ranged from 28 to 177. Only three studies reported the randomisation procedure used. None reported allocation concealment. Only two studies had a dropout rate of 0% and conducted an ITT analysis.
Diet-plus-exercise interventions were associated with significantly greater loss in weight or body mass index than diet-only interventions at the end of follow-up (difference in Cohen's d -0.25, 95% CI -0.36 to -0.14; 18 RCTs). Diet plus exercise interventions in comparison with diet-only interventions were associated with a significantly greater pooled weight loss (1.14kg, 95% CI 0.21 to 2.07; 10 RCTs) and a significant reduction in body mass index (0.50kg/m2, 95% CI 0.21 to 0.79; seven RCTs). The percentage of body fat loss was also significantly greater for the combined diet and exercise intervention as compared with the diet-only intervention (2%, 95% CI 0.65% to 3.5%; six RCTs). No significant statistical heterogeneity was found.
Meta-regression did not show statistical significant differences in results by baseline age, obesity, sex, population, comorbidities and duration of follow-up. However, there was a significantly greater loss in weight between the diet plus intervention group and the diet-only group in studies with longer intervention periods (p=0.03).
Results of other analyses were presented in the paper. There was no evidence of publication bias.