TRIUMPH 1 Retatrutide Results: The NEJM Obesity Trial, Dose by Dose
TRIUMPH 1 retatrutide results from the NEJM paper: 25.0% average weight loss on 12 mg over 80 weeks, serious side effects by dose, who stopped and why.
On this page
- How TRIUMPH-1 was set up
- TRIUMPH 1 retatrutide weight loss by dose
- Why NEJM says 25.0% and Lilly says 28.3%
- What happened to waist, blood pressure and blood fats
- Side effects, serious events and who stopped
- The 104-week extension and the subgroups
- Knee and sleep apnea groups inside TRIUMPH-1
- What TRIUMPH-1 doesn't tell you yet
In TRIUMPH-1, adults with obesity and no diabetes lost 25.0% of their body weight on average over 80 weeks on retatrutide 12 mg, against 3.9% on placebo, counting everyone who was randomized. That's the primary result in the New England Journal of Medicine paper published September 29, 2026. Lilly's better-known 28.3% comes from the same trial, counted as if nobody had stopped the drug. The TRIUMPH 1 retatrutide data also covers 2 smaller trials nested inside it, for knee arthritis and sleep apnea, and a 104-week extension.
Key takeaways
- The NEJM paper leads with 25.0% on 12 mg, not the 28.3% from Lilly's press release, because it counts people who stopped the drug.
- Going from 9 mg to 12 mg added 1.3 points of weight loss on the paper's main measure, while the share who quit because of side effects went from 6.9% to 11.3%.
- Low blood pressure was reported by 8.8% of people on 12 mg against 0.9% on placebo, and it was more common in people already taking blood pressure pills.
- People who stayed on for 104 weeks reached 30.3% on average, but only people with a BMI of 35 or more who had tolerated their full dose could join.
- As of October 31, 2026, ClinicalTrials.gov still shows no posted results, and no safety data from the 104-week extension has been published.
The headline number is only part of the paper. This page also covers the design, both sets of weight figures, the safety table Lilly reproduces from the paper (serious events, low blood pressure, deaths), and what's still missing as of October 31, 2026.
How TRIUMPH-1 was set up
TRIUMPH-1 (NCT05929066) is a double-blind, placebo-controlled Phase 3 trial run by Lilly. It randomized 2,339 adults 1:1:1:1 to weekly injections of retatrutide 4 mg, 9 mg or 12 mg or placebo, for 80 weeks: 584 people in each retatrutide group and 587 on placebo, per Lilly's medical information page. ClinicalTrials.gov lists 134 sites in 11 countries plus Puerto Rico, a start date of July 10, 2023 and completion on April 30, 2026.
To get in, you needed a BMI of 30 or more, or 27 or more with high blood pressure, abnormal blood fats, sleep apnea or heart disease, plus at least one failed attempt to lose weight by dieting. People with diabetes, past pancreatitis, a personal or family history of medullary thyroid cancer, prior obesity surgery, or weight loss drugs in the previous 90 days were excluded (ClinicalTrials.gov record).
The people who joined were heavier than in most obesity trials. Average starting weight was 112.7 kg (248.5 lb) and BMI 40.0, per Lilly's May 21, 2026 release, and 77.4% had a BMI of 35 or more. About 65% were women and the average age was about 48 in every arm (Lilly Medical Information). The design paper in Diabetes, Obesity and Metabolism says the trial aimed for about 80% at BMI 35 or more and capped women at about 70%.
Everyone started at 2 mg and stepped up every 4 weeks: 4 mg after one step, 9 mg through 4 and 6 mg, and 12 mg through 4, 6 and 9 mg. Doses could be cut permanently for gut side effects that didn't settle, for reaching a BMI of 22 or lower, or if someone felt they had lost too much. All arms got lifestyle counseling aimed at healthy food choices rather than calorie cuts, and at least 150 minutes a week of moderate activity with some strength work (design paper).
TRIUMPH 1 retatrutide weight loss by dose
The paper's primary result counts every person randomized, including those who stopped the drug or never reached their dose. On that measure, the treatment-regimen estimand, 9 mg and 12 mg beat placebo by 19.8 and 21.0 percentage points (P < 0.001 for both). The table adds kilograms and the share of people who crossed each threshold, with both ways of counting where Lilly gives them.
| At 80 weeks | 4 mg | 9 mg | 12 mg | Placebo |
|---|---|---|---|---|
| Average weight change, everyone randomized (NEJM primary) | -17.6% | -23.7% | -25.0% | -3.9% |
| Same, in kg (lb) | -19.8 kg (-43.7 lb) | -26.7 kg (-58.9 lb) | -28.2 kg (-62.1 lb) | -4.4 kg (-9.7 lb) |
| Lost 15% or more, everyone randomized | 56.9% | 76.8% | 79.5% | 11.4% |
| Lost 25% or more, everyone randomized | 25.0% | 46.7% | 53.0% | 2.6% |
| Lost 25% or more, if all stayed on drug | 27.8% | 52.9% | 62.5% | 2.2% |
| Lost 35% or more, everyone randomized | 5.7% | 18.3% | 21.1% | 0.2% |
| Lost 35% or more, if all stayed on drug | 5.9% | 20.8% | 27.2% | 0.3% |
Sources: NEJM abstract for the percentages in row 1; Lilly's May 21, 2026 release for kilograms; Lilly Medical Information for the threshold rows.
Counting everyone, about half the people on 12 mg (53.0%) lost a quarter of their body weight or more. Roughly 1 in 5 (21.1%) lost over a third. The step from 9 mg to 12 mg is small on the primary measure, 1.3 points, against 6.1 points for the step from 4 mg to 9 mg.
Lilly's releases lead with the efficacy estimand instead: what would have happened had everyone stayed on the drug without other weight treatments. On that count, 12 mg averaged 28.3%, or 31.9 kg (70.3 lb), and 9 mg averaged 25.9%.
Average weight lost by dose in TRIUMPH-1
80 weeks, 2,339 adults with obesity or overweight (efficacy estimand)
The Phase 3 results page puts these numbers next to the five other trials that have reported, and the retatrutide weight loss page covers what an average like this means for one person.
Why NEJM says 25.0% and Lilly says 28.3%
The gap is mostly dropouts, and they weren't spread evenly. Lilly's ADA 2026 presentation summary says about 64% of the placebo group finished the trial still on treatment, against about 75% to 87% in the retatrutide groups. People who stop a weight loss drug tend to regain, and people on placebo who give up don't lose much either, so the treatment-regimen estimand pulls the drug arms down more than the placebo arm.
Neither number is wrong. They answer different questions: "what does the drug do if you take it?" and "what happens to a group of people who are handed it?"
Our read: if you're trying to picture your own odds, the 25.0% figure is the more honest starting point, since somewhere between 1 in 8 and 1 in 4 people in the retatrutide arms didn't finish on the drug.
What happened to waist, blood pressure and blood fats
Weight wasn't the only thing that moved. These are efficacy estimand averages at 80 weeks from Lilly's medical information page, which reproduces the paper's tables:
| At 80 weeks, if all stayed on drug | 4 mg | 9 mg | 12 mg | Placebo |
|---|---|---|---|---|
| Waist | -16.3 cm | -21.8 cm | -24.1 cm | -3.6 cm |
| Systolic blood pressure | -8.5 mmHg | -11.3 mmHg | -12.3 mmHg | -1.1 mmHg |
| Triglycerides | -34.0% | -40.8% | -41.0% | -5.0% |
| Non-HDL cholesterol | -18.9% | -24.2% | -23.9% | -2.5% |
| Fasting insulin | -45.2% | -55.6% | -58.5% | -10.0% |
| hsCRP (an inflammation marker) | -57.9% | -63.5% | -63.8% | -23.5% |
On 12 mg, 65.3% of people ended with a BMI under 30 (pre-specified, not controlled for multiple testing), and Lilly's June 6 release adds that 33.3% got below 25. Among people who started at a BMI of 40 or more, 37.5% got under 30, a post hoc figure. These are risk factor changes, not heart attacks or strokes prevented. TRIUMPH-1 wasn't built to show that.
Side effects, serious events and who stopped
Gut side effects were the most common problem, as the NEJM abstract says, and they rose with dose. The table mixes Lilly's May release (nausea, vomiting, dysesthesia, stopping) with the safety table on Lilly's medical information page (serious events, low blood pressure, injection-site reactions), which counts the 2,335 people who took at least one dose.
| Over 80 weeks | 4 mg | 9 mg | 12 mg | Placebo |
|---|---|---|---|---|
| Nausea | 28.6% | 38.4% | 42.4% | 14.8% |
| Vomiting | 10.6% | 22.8% | 25.3% | 4.8% |
| Burning or oversensitive skin (dysesthesia) | 5.1% | 12.3% | 12.5% | 0.9% |
| Injection-site reactions | 5.5% | 8.9% | 12.2% | 3.8% |
| Low blood pressure (incl. dizziness on standing) | 2.7% | 5.3% | 8.8% | 0.9% |
| Serious adverse events | 7.7% | 7.7% | 10.5% | 5.5% |
| Stopped the drug because of side effects | 4.1% | 6.9% | 11.3% | 4.9% |
The stopping row is from Lilly's release; the medical information page's table gives 4.1%, 6.5%, 11.2% and 4.6%. Gut side effects alone caused 4.6% of people on 12 mg to stop, against 1.2% on placebo.
Low blood pressure tracked blood pressure pills. On 12 mg it was reported by 11.3% of people already taking them (27 of 239) and 7.0% of those who weren't, against 1.3% and 0.6% on placebo. If you take blood pressure medicine, that's a specific thing to raise with your doctor. Our read: with systolic pressure falling 12.3 mmHg on average, a blood pressure dose that was right at the start may be too much later on.
Six people died: 3 on 9 mg, 1 on 12 mg and 2 on placebo. Lilly's page lists 2 car accidents (one on placebo, one on 9 mg), a gunshot wound on placebo, 2 sudden deaths on 9 mg (1 judged not cardiovascular, 1 of undetermined cause), and on 12 mg a cardiovascular death in someone with known heart failure who had been off the study drug for 189 days. Adjudicated pancreatitis was rare: 1, 3 and 4 people on 4, 9 and 12 mg, against 2 on placebo. There were no cases of medullary thyroid cancer. The side effects page covers how long the gut symptoms last and what helps.
Everyone in TRIUMPH-1 got Lilly's study drug at blinded, fixed doses with trial staff watching. Vials sold online as retatrutide for sale aren't that product, and nothing in this trial tells you what's in them or how they behave.
The 104-week extension and the subgroups
TRIUMPH-1 kept 532 people on treatment to week 104. To qualify, you had to have started at a BMI of 35 or more and finished 80 weeks on the drug without stopping or a permanent dose cut. Everyone, including the placebo group, then had 24 more weeks on retatrutide, escalated blind to the highest dose they tolerated, 9 or 12 mg (Lilly's May release).
| At 104 weeks, extension group (start 121.7 kg, BMI 42.8) | 4 mg then max dose | 9 mg then max dose | 12 mg then max dose | Placebo then max dose |
|---|---|---|---|---|
| If all stayed on drug | -27.9% | -29.5% | -30.3% (-85.0 lb) | -19.2% |
| Everyone in the extension | -25.7% | -28.7% | -29.9% (-83.9 lb) | -18.9% |
These people had already shown they could tolerate the drug, so the 30.3% flatters what a fresh group would see. The former placebo group's 19.2% is measured from their week 0 weight, after 80 weeks on placebo and then 24 weeks on retatrutide. No side effect or dropout figures from the extension have been published.
Other subgroup data is thin. The design paper names BMI 35 or more as a pre-specified group and lists sex and prediabetes as randomization factors, but we found no published results split by sex, age or race in the abstract, the releases or Lilly's medical information page.
Knee and sleep apnea groups inside TRIUMPH-1
TRIUMPH-1 is a master protocol: 2 smaller trials ran inside it, each with its own primary result, and both met it.
- Knee osteoarthritis (574 people). On the paper's hybrid-treatment estimand, pain on the WOMAC scale (the abstract describes it as ranging from 1 to 10) fell 3.2, 3.5 and 3.6 points on 4, 9 and 12 mg, against 1.9 on placebo. Counting everyone randomized, it fell 3.4, 3.9 and 4.1 against 2.5. The stand-alone knee trial is covered on the TRIUMPH-4 page.
- Obstructive sleep apnea (243 people with an AHI of 15 or more, starting at 58.6 events per hour). Breathing pauses per hour fell 22.9, 34.3 and 31.7 on 4, 9 and 12 mg, against 9.9 on placebo, on the hybrid estimand. So 9 mg did better than 12 mg here. Lilly's "up to 36.1 events per hour" is a different, efficacy estimand figure. The substudy paper, published with TRIUMPH-2's sleep apnea group in NEJM on October 21, 2026, is covered on the sleep apnea page.
What TRIUMPH-1 doesn't tell you yet
There's no comparison with tirzepatide or semaglutide in this trial; placebo was the only comparator. TRIUMPH-1 also stopped at 80 weeks for most people, so it says nothing about what happens to weight after stopping, and it wasn't sized to count heart attacks or strokes. The abstract doesn't report heart rate change, which matters for a drug that acts on the glucagon receptor, and neither does Lilly's medical information page.
ClinicalTrials.gov still showed no posted results for TRIUMPH-1 on October 31, 2026, so the paper and Lilly's summaries are the only public tables.
On approval: Lilly last said, on September 29, 2026, that it plans to submit retatrutide to the FDA in the first quarter of 2027 as a Biologics License Application (BLA). On October 2, 2026, the FDA decided that retatrutide is a drug, not a biological product, so an application would need to be filed under section 505 of the Federal Food, Drug, and Cosmetic Act. Lilly's appeal on that question is pending in the Seventh Circuit, and we found no ruling as of October 31, 2026. No approved version exists yet, and the FDA approval page tracks the filing.
Frequently asked questions
What did TRIUMPH-1 show?
TRIUMPH-1 showed that retatrutide cut body weight by 17.6% on 4 mg, 23.7% on 9 mg and 25.0% on 12 mg over 80 weeks, against 3.9% on placebo, counting everyone randomized. Knee arthritis pain and sleep apnea also improved in the two groups nested inside the trial. Gut side effects were the most common problem, and more people stopped on 12 mg than on placebo.
How much weight did people lose on retatrutide in TRIUMPH-1?
On 12 mg, the average was 25.0% of starting weight, or 28.2 kg (62.1 lb), over 80 weeks counting everyone. Counted as if everyone had stayed on the drug, it was 28.3%, or 31.9 kg (70.3 lb). People started at an average of 112.7 kg (248.5 lb).
Is TRIUMPH-1 published?
Yes. The New England Journal of Medicine published it online on September 29, 2026 (Jastreboff AM et al., "Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity"). The sleep apnea substudies from TRIUMPH-1 and TRIUMPH-2 followed in the same journal on October 21, 2026. ClinicalTrials.gov had no posted results as of October 31, 2026.
How many people stopped retatrutide because of side effects in TRIUMPH-1?
Lilly's May 2026 release gives 4.1% on 4 mg, 6.9% on 9 mg and 11.3% on 12 mg, against 4.9% on placebo. Stomach and gut side effects were the most common reason. The 4 mg rate was lower than placebo's.
Why are there two different TRIUMPH-1 weight loss numbers?
They count dropouts differently. The treatment-regimen estimand, which the NEJM paper uses for its primary result, includes everyone randomized whether or not they kept taking the drug (25.0% on 12 mg). The efficacy estimand, which Lilly's releases lead with, estimates what would have happened had everyone stayed on it (28.3%).
Did anyone die in TRIUMPH-1?
Six people died: 3 on 9 mg, 1 on 12 mg and 2 on placebo, according to the safety table Lilly reproduces from the NEJM paper. The causes listed include 2 car accidents and a gunshot wound; the 12 mg death was a cardiovascular death in someone with known heart failure who had been off the study drug for 189 days.
Sources
- Jastreboff AM et al., Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity (TRIUMPH-1), N Engl J Med, online September 29, 2026. New England Journal of Medicine, 2026. doi.org
- Lilly's triple agonist, retatrutide, delivered powerful weight loss in pivotal Phase 3 obesity trial (TRIUMPH-1 topline, May 21, 2026). Eli Lilly and Company (PR Newswire), 2026. prnewswire.com
- What are the results of retatrutide from TRIUMPH-1 in participants with obesity or overweight without type 2 diabetes? (date of last review August 26, 2026; cites the NEJM paper). Lilly Medical Information, 2026. medical.lilly.com
- A Master Protocol to Investigate the Efficacy and Safety of LY3437943 Once Weekly in Participants Without Type 2 Diabetes Who Have Obesity or Overweight (TRIUMPH-1, NCT05929066). ClinicalTrials.gov, 2026. clinicaltrials.gov
- Giblin K et al., Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: rationale and design of the TRIUMPH registrational clinical trials, Diabetes Obes Metab 2026;28(1):83-93. Diabetes, Obesity and Metabolism, 2026. doi.org
- The First Phase 3 Obesity Study of Retatrutide in People with Obesity (TRIUMPH-1), ADA Scientific Sessions presentation summary, June 6, 2026. Eli Lilly and Company, 2026. lilly.com
- Lilly's triple agonist, retatrutide, drove substantial improvements in weight, A1C, knee osteoarthritis pain and obstructive sleep apnea (ADA 2026 presentations, June 6, 2026). Eli Lilly and Company (PR Newswire), 2026. prnewswire.com
- Grunstein RR et al., Retatrutide Once Weekly for Treatment of Obstructive Sleep Apnea (TRIUMPH-1-OSA and TRIUMPH-2-OSA), N Engl J Med, online October 21, 2026. New England Journal of Medicine, 2026. doi.org
- Lilly's triple agonist, retatrutide, delivered substantial weight loss and A1C reduction (TRIUMPH-2 detailed results, September 29, 2026). Eli Lilly and Company (PR Newswire), 2026. prnewswire.com
- FDA letter of October 2, 2026 on retatrutide's regulatory status, filed as Doc. 46-2 in Eli Lilly and Company v. Kennedy, 7th Cir. No. 26-1301. U.S. Food and Drug Administration (via CourtListener), 2026. storage.courtlistener.com
- Eli Lilly and Company v. Robert Kennedy Jr., 7th Cir. No. 26-1301 (docket). CourtListener, 2026. courtlistener.com
Dr. Juan Pablo Frías, MD
Physician-Scientist & Clinical Trialist • Endocrinology, Diabetes & Metabolism
Dr. Frías earned his M.D. from Vanderbilt University School of Medicine and completed his endocrinology fellowship at UC San Diego. A principal investigator on landmark incretin trials (including retatrutide, tirzepatide and semaglutide), he reviews all guides on Retatrutide360 for clinical accuracy, dosing safety and evidence fidelity.
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