The main finding
In one sentence: Three years after randomization, 38% of people who had gastric bypass and 24% who had sleeve gastrectomy had an HbA1c of 6.0% or less, compared with 5% of those on intensive medical therapy alone, in a small single-centre trial.
Group averages, not an individual prediction. A trial result describes what happened to a defined group over a defined time.
On this page
Why this study matters
Short randomized trials lasting one to two years had shown that bariatric surgery (an operation on the stomach or gut to help with weight loss) improves type 2 diabetes. The open question was whether the benefit lasts. This report follows the same 150 people from the original STAMPEDE trial out to three years. Canadian readers living with obesity and type 2 diabetes may want to know how the one-year results held up.
Who was in the study
The trial randomized 150 adults with obesity and uncontrolled type 2 diabetes. At the start, their average age was 48 years (standard deviation 8), 68% were women, and their average HbA1c was 9.3% (standard deviation 1.5). HbA1c is a blood test that reflects average blood sugar over about three months. Their average body mass index (BMI) was 36.0 (standard deviation 3.5). BMI is weight in kilograms divided by height in metres squared. A total of 91% completed 36 months of follow-up; the extracted data put this at 137 of 150 people (91.3%).
What the researchers did
This is an extension report, meaning the same people from the original trial were followed for longer. At the start, a computer had assigned each person by chance (randomized) to one of three groups: intensive medical therapy alone, medical therapy plus Roux-en-Y gastric bypass, or medical therapy plus sleeve gastrectomy. Gastric bypass reroutes food past most of the stomach; sleeve gastrectomy removes a large part of it. The trial was unblinded, meaning everyone knew their treatment, because surgery cannot be hidden. All groups received intensive medical therapy; the summary does not describe its details. The main outcome was an HbA1c of 6.0% or less.
What they found
At three years, the main outcome was met by 5% of the medical therapy group, 38% of the gastric bypass group (P less than 0.001 compared with medical therapy), and 24% of the sleeve gastrectomy group (P=0.01). A P value below 0.05 is usually treated as statistically significant, meaning the difference is unlikely to be due to chance. The summary we reviewed does not report confidence intervals.
Weight results also favoured surgery. Average weight loss from the start was 24.5% (standard deviation 9.1) with gastric bypass, 21.1% (standard deviation 8.9) with sleeve gastrectomy, and 4.2% (standard deviation 8.3) with medical therapy alone (P less than 0.001 for both surgical comparisons) (R32-C104).
| Result at 3 years | Medical therapy alone | Gastric bypass | Sleeve gastrectomy |
|---|---|---|---|
| HbA1c 6.0% or less | 5% | 38% | 24% |
| Average weight loss | 4.2% | 24.5% | 21.1% |
People in the surgical groups used fewer glucose-lowering medicines, including insulin, than people in the medical therapy group. Quality-of-life scores were significantly better in both surgical groups than in the medical therapy group. The summary does not give the quality-of-life numbers.
Side effects and people who stopped
The summary reports no major late surgical complications. The extracted data show that 8 people in the medical therapy group and 1 in the sleeve gastrectomy group withdrew early, and 4 people overall were lost to follow-up. Side effects were not reported in detail in the summary we reviewed.
What this study does not tell you
- The trial was small (150 people) and ran at one centre. Small trials can give results that do not repeat elsewhere.
- Because the trial was unblinded, expectations could have influenced quality-of-life reports.
- The three-year results are based on the people who were available for assessment. The summary does not describe how missing results were handled.
- The medical therapy in this trial predates newer diabetes and weight-management medicines. STAMPEDE does not compare surgery with those medicines.
- The one-year and five-year STAMPEDE reports describe the same people. They are not separate confirmations.
- The trial was funded in part by a maker of surgical devices.
What it means in Canada
STAMPEDE is often cited in Canadian discussions of treating type 2 diabetes in people living with obesity. It does not tell you whether surgery is right for you, and it does not compare surgery with the medicines used today. For information on medicines, see semaglutide in Canada and tirzepatide in Canada. For questions about what provincial plans pay for, see public drug coverage by province.
Common questions
What share of people reached the blood-sugar target at three years in STAMPEDE?
An HbA1c of 6.0% or less was met by 5% of the medical therapy group, 38% of the gastric bypass group, and 24% of the sleeve gastrectomy group.
How much weight did people lose after three years in the STAMPEDE trial?
Average weight loss was 24.5% with gastric bypass, 21.1% with sleeve gastrectomy, and 4.2% with intensive medical therapy alone.
How many people completed three years of follow-up in STAMPEDE?
Of 150 people randomized, 137 (91.3%) were assessed at three years. Eight medical therapy participants and one sleeve gastrectomy participant withdrew early.
Related reading
Other studies in this library that bear on the same question.
STAMPEDE: bariatric surgery versus medical therapy for type 2 diabetes
STAMPEDE at five years: surgery versus medical therapy
Ten years after weight-loss surgery: the Swedish Obese Subjects study
DiRECT at two years: diabetes remission with a diet programme
Source
Original paper: Philip R Schauer, STAMPEDE 3-year, The New England journal of medicine, 2014. PubMed: https://pubmed.ncbi.nlm.nih.gov/24679060/. DOI: https://doi.org/10.1056/NEJMoa1401329. Funding: The trial was funded by Ethicon, LifeScan, the Cleveland Clinic and the National Institutes of Health. How we summarized it: full text and extracted data.
This page explains a published study. It is not medical advice and does not describe whether a medicine is right for you. Talk to your doctor, nurse practitioner or pharmacist about your own situation. Reviewed and signed by two pharmacists registered in British Columbia, 2026-09-18.
Evidence records behind this page
Each record is a row in the clinical evidence file, taken from the published paper named above. The caution column is the limit the researcher recorded for that number.
This table scrolls sideways.
| Record | What the paper reports | Type | Population | Caution | Source |
|---|---|---|---|---|---|
| R32-C104 | At 3 years in STAMPEDE, mean weight losses were 24.5% with gastric bypass,21.1% with sleeve gastrectomy and 4.2% with intensive medical therapy alone. | direct evidence | Adults with obesity and uncontrolled T2D | Small single-centre unblinded trial; treatment era limits comparisons to modern medication care. Primary 22449319 and 5-year 28199805 share participants. | PubMed 24679060 |