Tirzepatide Achieves Up to 22.4% Weight Loss in Japanese Adults — 100% of 10 mg Group Lost ≥5% | Research

The takeaway

Tirzepatide achieved 12-22.4% weight loss in Japanese adults with obesity, with 100% of the 10 mg group achieving ≥5% reduction and significant cardiometabolic improvements over 72 weeks.

100% response at 10 mg
Every single Japanese participant on tirzepatide 10 mg achieved at least 5% weight loss — an unprecedented 100% responder rate

What the researchers found

Japanese adults (n=102): tirzepatide 5/10/15 mg achieved -12.0/-22.4/-22.1% weight loss vs -0.3% placebo at 72 weeks. ≥5% loss: 91.7/100/96.6% vs 15.4%. Significant cardiometabolic improvements. No new safety signals.

Why it matters

Japan has rising obesity rates. Demonstrating tirzepatide's exceptional efficacy specifically in Japanese adults supports its clinical adoption in Asia.

How the study worked

Prespecified subpopulation analysis of 102 Japanese adults from the SURMOUNT-1 trial (NCT04184622), tirzepatide 5/10/15 mg vs placebo for 72 weeks.

What this study cannot tell us

Subgroup analysis of 102 from larger trial. Small sample per dose group. Post-hoc ethnic comparison limited.

How to read the evidence

Prespecified subpopulation analysis from pivotal Phase 3 RCT. Small but rigorous.

When this study was published

Published in 2025 from SURMOUNT-1 trial.

The bigger picture

Tirzepatide's performance in Japanese adults exceeds the overall trial population, consistent with meta-analyses showing greater incretin benefit in Asian populations.

Questions still open

Why does tirzepatide appear more effective in Japanese/Asian populations?
Would lower doses be sufficient for Japanese patients?
How does this compare to semaglutide Japanese data?

Common questions

Does tirzepatide work well for Japanese patients?

Exceptionally well. 100% of Japanese participants on the 10 mg dose lost at least 5% body weight, with average losses of 22.4% — among the best results seen for any obesity drug.

Why might Asian patients respond better to tirzepatide?

The reasons are being studied, but may relate to differences in body composition, GLP-1/GIP receptor biology, or metabolic processing. This is consistent with other studies showing greater GLP-1 drug cardiovascular benefits in Asian populations.

Read the original research

Efficacy and Safety of Tirzepatide in Japanese Participants With Obesity: A Subpopulation Analysis of the SURMOUNT-1 Trial.

Obesity (Silver Spring, Md.), 34(3), 608-621

View on PubMed ↗Publisher’s paper ↗

Citation

Ishigaki, Yasushi; Yamada, Masamichi; Shingaki, Tomotaka; Oura, Tomonori; Shimomura, Iichiro. (2026). Efficacy and Safety of Tirzepatide in Japanese Participants With Obesity: A Subpopulation Analysis of the SURMOUNT-1 Trial.. Obesity (Silver Spring, Md.), 34(3), 608-621. https://doi.org/10.1002/oby.70131