Weight Loss With GLP-1 Agonists in Nondiabetic Adults: Systematic Review and Network Meta-Analysis.
This systematic review and network meta-analysis compared the weight-loss efficacy and safety of three FDA-approved agents—tirzepatide (a dual GIP/GLP-1 agonist), semaglutide, and liraglutide—in non-diabetic adults with obesity. Researchers searched four major databases through May 2025 and identified 15 Phase 3 RCTs encompassing 14,059 patients. Using a frequentist random-effects network meta-analysis, the authors found that all three agents produced statistically significant body weight reductions compared to placebo. Ranking by magnitude of effect, the highest tolerated dose of tirzepatide demonstrated the greatest weight reduction, followed by lower tirzepatide doses, then semaglutide, and finally liraglutide. On the safety side, tirzepatide and semaglutide were each associated with a higher risk of any adverse event compared to placebo, while liraglutide was not. The authors note that the analysis was limited to Phase 3 RCTs and did not assess long-term outcomes such as weight regain after discontinuation, metabolic endpoints, cost-effectiveness, or patient preferences, which they identify as priorities for future research.
Why this grade: The study synthesizes 15 Phase 3 RCTs with over 14,000 human participants using a rigorous network meta-analysis methodology, providing strong pooled human evidence; limitations include indirect comparisons across trials and lack of long-term follow-up data.
Objective Two glucagon-like peptide-1 receptor agonists (GLP-1 RAs) (semaglutide and liraglutide) and one dual agonist (tirzepatide) are FDA-approved for weight loss in adults with obesity without type 2 diabetes mellitus. This systematic review and network meta-analysis aims to compare the efficacy of these agents against each other. Methods A comprehensive search of PubMed/MEDLINE, Embase, Web of Science, and Cochrane Library was conducted from inception to May 2025. Phase 3 randomized controlled trials (RCTs) in adult patients (≥ 18 years) with at least one arm of tirzepatide, semaglutide, or liraglutide were included. A frequentist random-effects network meta-analysis was performed using R 4.3.3. Results Of 1420 articles identified, 15 RCTs with 14,059 patients were included. All agents significantly reduced body weight compared to placebo. The largest reduction occurred with the maximum tolerated dose of tirzepatide, followed by tirzepatide 15 mg and 10 mg, semaglutide 2.4 mg, tirzepatide 5 mg, and liraglutide 3 mg. Tirzepatide and semaglutide were associated with a higher risk of any adverse event compared with placebo, whereas liraglutide was not. Conclusions Tirzepatide, particularly at higher doses, provides the greatest weight reduction in adults without diabetes. Future studies should evaluate discontinuation, weight regain, metabolic outcomes, cost-effectiveness, and patient preferences.
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