Trial review
STEP-1: Semaglutide 2.4 mg for Weight Management, Explained
How much weight does semaglutide 2.4 mg produce in adults with obesity and without diabetes?
Direct answer
STEP-1 was a randomised, double-blind, placebo-controlled, phase 3 funded by Novo Nordisk. Mean weight change of −14.9% against −2.4% on placebo; about 86% reached 5% or more, about 51% reached 15% or more. That figure belongs to the population, dose and 68 weeks shown below, and describes a group average rather than a prediction for any individual.
STEP-1 at a glancepublished, peer-reviewed
| Design | Randomised, double-blind, placebo-controlled, phase 3 |
|---|---|
| Population | Adults with BMI 30 or above, or 27 or above with at least one weight-related comorbidity, without diabetes |
| Sample size | 1961 |
| Intervention | Semaglutide |
| Comparator | Placebo, both arms with lifestyle intervention |
| Duration | 68 weeks |
| Primary endpoint | Percentage change in body weight |
| Main result | Mean weight change of −14.9% against −2.4% on placebo; about 86% reached 5% or more, about 51% reached 15% or more |
NCT NCT03548935 · DOI 10.1056/NEJMoa2032183 · PMID 33567185Last source check: 2026-08-03
Show this figure as a table
| Step | Stage | What happens |
|---|---|---|
| 1 | Who was eligible | Adults with BMI 30 or above, or 27 or above with at least one weight-related comorbidity, without diabetes |
| 2 | What they received | Semaglutide |
| 3 | What it was compared against | Placebo, both arms with lifestyle intervention |
| 4 | For how long | 68 weeks |
| 5 | What was measured first | Percentage change in body weight |
| 6 | What the group average was | Mean weight change of −14.9% against −2.4% on placebo; about 86% reached 5% or more, about 51% reached 15% or more |
| 7 | What it does not tell you | A group average is not a prediction for any individual reader. |
Strip any step and the result stops meaning what the trial found.
Show this figure as a table
| Item | Weight change | Evidence |
|---|---|---|
| Semaglutide 2.4 mg | 15% | published, peer-reviewed |
| Placebo | 2% | published, peer-reviewed |
Group means under trial conditions with lifestyle intervention. Not a prediction for any individual reader.
Show this figure as a table
| Item | Mean reduction | Evidence |
|---|---|---|
| Tirzepatide 15 mg (SURMOUNT-1) | 21% | Verified |
| Oral semaglutide 25 mg, adherent (OASIS 4) | 17% | Verified |
| Injectable semaglutide 2.4 mg (SURMOUNT-5) | 14% | Verified |
| Oral semaglutide 25 mg, treatment-policy (OASIS 4) | 14% | Verified |
| Orforglipron 17.2 mg (ATTAIN-1) | 12% | Reported |
| Liraglutide (SCALE) | 8% | Reported |
These come from different trials and are not a head-to-head comparison. Durations differ (64 to 72 weeks) and estimands differ. Only SURMOUNT-5 compared two of these drugs directly.
| Product | Starting self-pay price | Reported mean reduction | Trial |
|---|---|---|---|
| Zepbound (tirzepatide) injectable | $299/mo direct | about 20.9% at 15 mg | SURMOUNT-1, 72 weeks |
| Wegovy pill (oral semaglutide 25 mg) | $149/mo starting dose | 13.6–16.6% depending on estimand | OASIS 4, 64 weeks |
| Wegovy injectable (semaglutide 2.4 mg) | $349/mo maintenance | about 13.7% | SURMOUNT-5, 72 weeks |
| Foundayo (orforglipron) | $149/mo starting dose | about 11–12.4% at 17.2 mg | ATTAIN-1, 72 weeks |
Both $149 products are the least effective approved options in this table. That does not make them bad choices — it makes a price comparison that omits efficacy an incomplete one.
Frequently asked questions
Does this apply to compounded versions?
No. The trial studied an FDA-approved product at studied doses.
Is this drug as effective as tirzepatide?
By mean reduction across separate trials, no. The efficacy ladder above sets out the figures with the trial that produced each one.
Related on this site
- Research hubResearch
- SURMOUNT-1 Tirzepatide Trial ExplainedResearch
- SURMOUNT-3 Tirzepatide Trial ExplainedResearch
- SURMOUNT-4: Weight Maintenance and Tirzepatide WithdrawalResearch
- Provider ranking methodologyCore & Trust
- GLP-1 total cost calculatorTools
- Download the pricing recordsData
- Tirzepatide and Type 2 Diabetes PreventionResearch
- Tirzepatide and PCOS: What Evidence Exists?Research
- Tirzepatide and Heart Failure With Preserved Ejection FractionJournal
Related coverage
Cite this pageCC BY 4.0
GLP-1 Tirzepatide Rank. “STEP-1: Semaglutide 2.4 mg for Weight Management, Explained.” S.J Partners LLC, 2026-08-03. https://glp1tirzepatiderank.com/research/step-1/
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