Tirzepatide achieves 4-5% more weight loss than semaglutide with fewer GI side effects in indirect comparison | Research

The takeaway

Indirect comparison of phase 3 trials shows tirzepatide 10-15 mg achieves 4-5.4% greater weight loss and additional 0.4% HbA1c reduction versus semaglutide 2.4 mg, with fewer gastrointestinal side effects.

4-5.4% more weight loss
Tirzepatide outperforms semaglutide in indirect phase 3 comparison with fewer GI side effects—supporting dual GLP-1/GIP agonism

What the researchers found

Tirzepatide vs semaglutide (ITT): 4% (10mg) and 5.4% (15mg) additional weight loss without T2D; additional -0.4% HbA1c with T2D; fewer GI side effects with tirzepatide.

Why it matters

Head-to-head data is limited. This indirect comparison helps clinicians choose between the two most important obesity drugs, showing tirzepatide's advantages in both efficacy and tolerability.

How the study worked

Systematic review of PubMed through December 2024. Indirect treatment comparison of matched STEP (semaglutide) and SURMOUNT (tirzepatide) phase 3 RCTs.

What this study cannot tell us

Indirect comparison—not a head-to-head trial. Some differences between trial populations may exist. ITT analysis may underestimate on-treatment differences.

How to read the evidence

Systematic review with indirect treatment comparison of phase 3 RCTs. Good methodology but indirect comparisons are inherently weaker than head-to-head trials.

When this study was published

Published in 2025; literature through December 2024.

The bigger picture

Tirzepatide's dual GLP-1/GIP mechanism appears to provide greater efficacy with better tolerability than pure GLP-1 agonism, suggesting that targeting multiple incretin pathways is the future of obesity pharmacotherapy.

Questions still open

Will the ongoing SURMOUNT-5 head-to-head trial confirm these indirect findings?
Is the GI tolerability advantage due to GIP receptor agonism?
Do the efficacy differences translate to better long-term health outcomes?

Common questions

Which is better: tirzepatide or semaglutide?

This indirect comparison suggests tirzepatide produces 4-5% more weight loss than semaglutide with fewer stomach side effects. However, this is not from a direct head-to-head study. Both are highly effective; the choice may depend on availability, cost, and individual tolerance.

Why might tirzepatide work better?

Tirzepatide activates both GLP-1 and GIP receptors (dual agonist), while semaglutide only activates GLP-1. The additional GIP pathway may enhance metabolic effects and paradoxically reduce GI side effects by modulating gut hormones more broadly.

Read the original research

Comparative efficacy and safety of semaglutide 2.4 mg and tirzepatide 5-15 mg in obesity with or without type 2 diabetes: A systematic review of Phase 3 clinical trials.

Diabetes & metabolic syndrome, 19(3), 103212

View on PubMed ↗Publisher’s paper ↗

Citation

Singh, Akriti; Singh, Awadhesh Kumar; Singh, Ritu; Misra, Anoop. (2025). Comparative efficacy and safety of semaglutide 2.4 mg and tirzepatide 5-15 mg in obesity with or without type 2 diabetes: A systematic review of Phase 3 clinical trials.. Diabetes & metabolic syndrome, 19(3), 103212. https://doi.org/10.1016/j.dsx.2025.103212