Combined exercise and dietary interventions for body composition in adults with overweight or obesity: a comparator-stratified systematic review and meta-analysis of randomized trials

Objective This study aimed to evaluate the effects of combined exercise-dietary interventions on body weight (BW), body mass index (BMI), fat-free mass (FFM), and fat mass percentage (FM%) in adults with overweight or obesity compared with randomized comparators. Methods PubMed, Embase, Web of Science, and the Cochrane Library were searched on 28 September 2026. Twenty-three reports representing 21 unique parent trials were included. Post-intervention arm data were synthesized as comparator-specific mean differences using restricted maximum likelihood random-effects models with truncated Hartung–Knapp confidence intervals, Tau-squared, and 95% prediction intervals. Cross-comparator and hierarchical parent-trial models were used as sensitivity analyses. Risk of bias was assessed using the revised Cochrane Risk of Bias tool for randomized trials (RoB 2), and certainty of evidence was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. Results The BW analysis included 1,303 participant observations. Against dietary-only controls, combined interventions reduced BW by −4.49 kg (95% confidence interval −8.05 to −0.92), and reduced BMI by −1.50 kg m −2 (−2.67 to −0.34), but both prediction intervals crossed the null. Exercise-only comparisons were imprecise, while active dietary and exercise comparisons and minimal guidance comparisons each relied on one report. No comparator stratum showed reliable improvement in FFM or FM%. Cross-comparator sensitivity estimates favored combined interventions for BW and BMI, but every prediction interval crossed the null. Certainty of the estimates was very low for all outcomes. Conclusion Combined interventions may reduce BW and BMI compared with trial-specific comparators in comparisons with dietary-only controls, but heterogeneity and sparse strata limit certainty. The evidence did not establish FFM preservation, the superiority of one dietary intervention type, or clinical importance. Systematic review registration https://www.crd.york.ac.uk/PROSPERO/ , identifer CRD420251174901.