SOURCE-LINKED STUDY SUMMARY
Semaglutide Weight Loss: STEP 1’s 14.9% Result Explained
PED EVIDENCE INTERPRETATION
How much weight loss did STEP 1 show?
At 68 weeks, average weight change was −14.9% with semaglutide versus −2.4% with placebo in adults with overweight or obesity, without diabetes. Both groups received lifestyle intervention; these are average results, not guaranteed individual outcomes. [1]
- Design
- Double-blind randomized STEP 1 trial; 1,961 adults
- Population
- Overweight with a weight-related condition, or obesity; no diabetes
- Comparison
- Weekly subcutaneous semaglutide 2.4 mg vs placebo; both with lifestyle intervention
- Duration
- 68 weeks
The evidence at a glance
| Outcome | Semaglutide | Placebo | Interpretation |
|---|---|---|---|
| Mean body-weight change [1] | −14.9% | −2.4% | Difference −12.4 percentage points; 95% CI −13.4 to −11.5 |
| Lost at least 5% [1] | 86.4% | 31.5% | Reported week-68 responder proportions |
| Lost at least 15% [1] | 50.5% | 4.9% | Reported week-68 responder proportions |
| Stopped because of gastrointestinal events [1] | 4.5% | 0.8% | Discontinuation due to these events, not all adverse events |
OUR READING OF THE EVIDENCE
What this changes
This trial establishes a substantial average weight-loss effect beyond lifestyle support alone in its eligible population. [1]
What it does not establish
It does not establish outcomes after withdrawal, identical effects in type 2 diabetes, or how much of the lost weight was contractile muscle. [1]
Put it in context
Read what happened after treatment ended
The separate STEP 1 extension examines the maintenance question. Treatment-period efficacy and post-withdrawal outcomes need to be read together, with attention to different study populations and analysis methods.
Read the related study summarySources and transparency
Funded by Novo Nordisk. Abstract-based interpretation; not an independent assessment of all adverse events or methodological quality. [1]
Questions this study helps answer
Was the 14.9% loss all body fat?
No. The headline outcome is body weight. It does not partition the loss into fat, muscle and water or establish how much strength changed. [1]
Did STEP 1 include people with type 2 diabetes?
No. This trial excluded diabetes. Results in a population with type 2 diabetes must be assessed using the relevant trials rather than assuming the same average weight loss. [1]
Original compact summary and study details
- What was studied
- Randomized trial testing semaglutide versus placebo, both alongside lifestyle intervention, over 68 weeks.
- Who / model studied
- 1961 adults with overweight or obesity and no diabetes.
- Studied dose & schedule
- Dose and schedule have not yet been extracted for this summary.
- What the study found
- The two main outcomes favored semaglutide: average weight fell 14.9% versus 2.4%, and 86.4% versus 31.5% lost at least 5%. Nausea and diarrhea were common. Digestive side effects caused treatment withdrawal in 4.5% versus 0.8%.
- Limitations & context
- Study limitations were not stated in the abstract. Methodological quality has not been appraised.
Read summary source ↗ · Prepared 9/16/2026 · AI-assisted, source-based summary
Review record & corrections
Summary prepared: . Source scope: abstract. This is an AI-assisted source summary, not an independent clinician sign-off.
No public field-by-field revision history is available for this card yet. The date above is the summary date, not proof that every field was updated then.
Inspect the source · Correction policyResearch findings apply to the population and conditions studied. This educational summary is not a treatment recommendation or a formal assessment of study quality.
Original publication ↗ · DOI: 10.1056/nejmoa2032183