Comparing semaglutide, liraglutide, orlistat, and phentermine for obesity: a systematic review
A systematic review comparing obesity drugs found all four agents—semaglutide, liraglutide, orlistat, and phentermine—offer distinct weight loss benefits, with GLP-1 agonists showing the strongest efficacy but GI side effects requiring personalized treatment approaches.
Quick Facts
What This Study Found
All four agents provide weight loss benefits through distinct mechanisms. GLP-1 agonists (semaglutide, liraglutide) show superior efficacy but cause GI side effects. Orlistat reduces fat absorption with GI discomfort. Phentermine suppresses appetite but has dependency potential. Emerging dual/triple agonists show promise.
Key Numbers
Compares semaglutide, liraglutide, orlistat, phentermine, plus emerging agents: setmelanotide, amycretin, retatrutide, cagrilintide, and cotadutide. Reviews mechanisms, dosing, efficacy, safety, and comorbidity effects.
How They Did This
Systematic literature review comparing mechanisms, dosing, efficacy, safety profiles, and comorbidity impact of semaglutide, liraglutide, orlistat, phentermine, and emerging obesity agents.
Why This Research Matters
With multiple obesity medications now available, clinicians need comparative data to match the right drug to each patient. This review provides a comprehensive comparison to guide personalized treatment selection based on efficacy needs, side effect tolerance, and comorbidity profiles.
The Bigger Picture
The obesity pharmacotherapy landscape is rapidly expanding, particularly with GLP-1-based peptide drugs. This comparative review helps contextualize where peptide therapies fit among all available options and highlights the growing dominance of incretin-based approaches in weight management.
What This Study Doesn't Tell Us
Literature review without meta-analysis or quantitative pooling. Head-to-head trial data is limited for many comparisons. Emerging agents have less mature evidence. Long-term comparative data is scarce.
Questions This Raises
- ?How do next-generation multi-agonists (retatrutide, amycretin) compare to current best-in-class semaglutide?
- ?Which patient profiles benefit most from non-GLP-1 options like orlistat or phentermine?
- ?What is the optimal duration of pharmacotherapy for sustained weight loss?
Trust & Context
- Key Stat:
- Multiple options, different profiles GLP-1 agonists lead in efficacy, but each obesity drug class offers distinct advantages depending on patient needs and tolerability
- Evidence Grade:
- Systematic review of existing literature. Provides comprehensive overview but without quantitative meta-analysis. Quality depends on underlying studies reviewed.
- Study Age:
- Published in 2025; includes emerging agents in development pipeline.
- Original Title:
- Comparative Effectiveness of Semaglutide, Liraglutide, Orlistat, and Phentermine for Weight Loss in Obese Individuals: A Systematic Review.
- Published In:
- Cureus, 17(3), e80321 (2025)
- Authors:
- Patel, Jay P, Hardaswani, Daksh, Patel, Jaykumar, Saiyed, Faizanali, Goswami, Rushita J, Saiyed, Taskin I, Patel, Harshkumar, Amin, Trishul H
- Database ID:
- RPEP-12978
Evidence Hierarchy
Analyzes all available research on a topic using a structured method.
What do these levels mean? →Frequently Asked Questions
Which weight loss drug works best?
GLP-1 receptor agonists like semaglutide generally show the greatest weight loss in clinical trials. However, the "best" choice depends on individual factors: some patients may not tolerate GI side effects, may prefer oral medication, or may have conditions that favor one drug over another.
Can weight loss drugs be used long-term?
GLP-1 agonists and orlistat are approved for long-term use, while phentermine is typically for short-term use due to dependency concerns. The review emphasizes that all medications work best when combined with diet and exercise changes for sustainable results.
Read More on RethinkPeptides
Cite This Study
https://rethinkpeptides.com/research/RPEP-12978APA
Patel, Jay P; Hardaswani, Daksh; Patel, Jaykumar; Saiyed, Faizanali; Goswami, Rushita J; Saiyed, Taskin I; Patel, Harshkumar; Amin, Trishul H. (2025). Comparative Effectiveness of Semaglutide, Liraglutide, Orlistat, and Phentermine for Weight Loss in Obese Individuals: A Systematic Review.. Cureus, 17(3), e80321. https://doi.org/10.7759/cureus.80321
MLA
Patel, Jay P, et al. "Comparative Effectiveness of Semaglutide, Liraglutide, Orlistat, and Phentermine for Weight Loss in Obese Individuals: A Systematic Review.." Cureus, 2025. https://doi.org/10.7759/cureus.80321
RethinkPeptides
RethinkPeptides Research Database. "Comparative Effectiveness of Semaglutide, Liraglutide, Orlis..." RPEP-12978. Retrieved from https://rethinkpeptides.com/research/patel-2025-comparative-effectiveness-of-semaglutide
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkPeptides research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.