STEP 1 — Once-weekly semaglutide in adults with overweight or obesity
In plain English
The trial that launched the GLP-1 weight-loss era: 1,961 adults with obesity but without diabetes were randomised to weekly injectable semaglutide 2.4 mg or placebo, both with lifestyle advice, for 68 weeks. The semaglutide group lost an average of 14.9% of body weight versus 2.4% on placebo — a magnitude previously achievable only with bariatric surgery, and far beyond any diet or earlier drug. It reset expectations for what pharmacological weight loss could deliver.
Why it matters
Weekly semaglutide produced ~15% average body-weight loss versus ~2% on placebo over 68 weeks.
Informs: Weight Loss·Diabetes
Provenance
- Design
- Randomised controlled trial
- Sample size (n)
- 1,961
- Follow-up
- 1.3 years
- Peer-reviewed
- Yes
- Replications
- 3
- Funding
- Industry-funded
- Funders
- Novo Nordisk
- Institutions
- University of Liverpool, University College London, University of Texas Southwestern Medical Center
decades.plus score
A transparent 0–100 weighted sum across six components. Higher scores reflect bigger, cleaner, more replicated work.
Caveats
Funded and run by the drug's manufacturer, Novo Nordisk, which our score penalises. Weight tends to return after stopping the drug (shown in the STEP-1 extension), gastrointestinal side effects are common, and the trial measured weight, not long-term health outcomes — the cardiovascular evidence came later in SELECT.
