SURMOUNT-1
Tirzepatide's pivotal weight trial: 22.5% average loss at the 15 mg dose over 72 weeks, with 57% losing 20%+.
SURMOUNT-1 (Jastreboff et al., NEJM 2022) tested weekly tirzepatide in 2,539 adults with obesity, without diabetes, for 72 weeks. The 15 mg dose averaged 22.5% body-weight loss by the efficacy estimand — the largest figure any medication had posted — with 57% of participants losing at least 20% of their body weight, territory previously associated with surgery.
Reading it well requires the fine print: averages differ by estimand (treatment-regimen analysis shows 20.9%), results came alongside diet and activity changes, and lower doses posted lower numbers. SURMOUNT-1 is the citation behind every "up to 22.5%" on a tirzepatide page, including ours, and comparing it to STEP 1 across different trials is directional context, not a head-to-head race.
This glossary entry is general information, not medical advice, and is written to be consistent with FDA prescribing information and primary trial publications as of its last review. Always consult a licensed healthcare provider for personal medical decisions.
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