Retatrutide’s Phase 3 results are now large enough that one number no longer describes the drug.
Depending on which trial you look at, the highest-dose retatrutide group lost an average of about 20.8%, 22.6%, 28.3%, or 28.7% of body weight.
Those differences are not contradictions.
They come from four trials that studied very different people.
TRIUMPH-1 enrolled adults with obesity or overweight without type 2 diabetes. TRIUMPH-2 specifically enrolled people with type 2 diabetes. TRIUMPH-3 required severe obesity and established cardiovascular disease. TRIUMPH-4 required knee osteoarthritis and excluded diabetes.
The studies also differed in duration, doses, endpoints, and clinical objectives.
So the useful question is not simply, “How much weight does retatrutide cause people to lose?”
It is:
What happened in each Phase 3 population, and how comparable are those results?
TL;DR
TRIUMPH-1 produced average weight loss of up to 28.3% at week 80.
TRIUMPH-2, in adults with type 2 diabetes, produced up to 20.8% at week 80.
TRIUMPH-3, in adults with severe obesity and established cardiovascular disease, produced up to 22.6% at week 80.
TRIUMPH-4 produced up to 28.7% at week 68 while also substantially reducing knee osteoarthritis pain.
The easiest mistake is treating those percentages as though they came from the same experiment.
They did not.
TRIUMPH-1 Through TRIUMPH-4 Side by Side
| Trial | Population | Duration | Doses | Highest Reported Weight Reduction* | Placebo |
|---|---|---|---|---|---|
| TRIUMPH-1 | Obesity/overweight, no T2D | 80 weeks | 4, 9, 12 mg | -28.3% | -2.2% |
| TRIUMPH-2 | Obesity/overweight + T2D | 80 weeks | 4, 9, 12 mg | -20.8% | -4.0% |
| TRIUMPH-3 | BMI ≥35 + established CVD | 80 weeks | 9, 12 mg | -22.6% | -3.2% |
| TRIUMPH-4 | Obesity/overweight + knee OA, no diabetes | 68 weeks | 9, 12 mg | -28.7% | -2.1% |
*Efficacy estimand reported by Lilly.
These numbers already show why trial population matters.
TRIUMPH-1: The Broad Obesity Population
TRIUMPH-1 is the study most people mean when they quote the headline Phase 3 retatrutide weight-loss number.
The trial randomized 2,339 participants with obesity or overweight. They did not have type 2 diabetes.
At week 80, efficacy-estimand body-weight changes were:
| Dose | Average Weight Change |
|---|---|
| 4 mg | -19.0% |
| 9 mg | -25.9% |
| 12 mg | -28.3% |
| Placebo | -2.2% |
The average baseline body weight was about 112.7 kg, or 248.5 pounds, with an average BMI of 40.0 kg/m².
The dose-response pattern is clear.
Moving from 4 mg to 9 mg was associated with a substantial increase in average weight reduction. Moving from 9 mg to 12 mg added a smaller additional reduction.
The trial also showed how far into the distribution some participants went.
At 12 mg, 62.5% reached at least 25% weight loss, 45.3% reached at least 30%, and 27.2% reached at least 35% under the efficacy estimand.
The 104-Week TRIUMPH-1 Extension Matters
TRIUMPH-1 also included a prespecified extension in 532 participants who had started the study with BMI of at least 35 and had tolerated study treatment.
At week 104, the group originally assigned to 12 mg had reached an average reduction of 30.3% under the efficacy estimand.
That result should not be treated as though all 2,339 original participants were followed under exactly the same conditions for 104 weeks.
The extension was a selected subgroup.
Still, it is important because it suggests that average weight loss had not necessarily reached its maximum by week 80 in participants with more severe baseline obesity.
TRIUMPH-2: Type 2 Diabetes Changes the Picture
TRIUMPH-2 enrolled 1,152 adults with obesity or overweight and type 2 diabetes.
That is a major population difference.
At week 80, Lilly reported:
| Dose | Average Weight Change |
|---|---|
| 4 mg | -12.7% |
| 9 mg | -19.1% |
| 12 mg | -20.8% |
| Placebo | -4.0% |
Average baseline BMI was 38.2 kg/m² and average body weight was 106.4 kg.
The 12 mg result is almost eight percentage points lower than the 12 mg result in TRIUMPH-1.
That does not mean TRIUMPH-2 shows retatrutide suddenly became much less pharmacologically active.
It means the studies examined different populations.
Type 2 diabetes status, baseline metabolic health, background treatment, study population characteristics, and other variables can all affect observed weight change.
This is why cross-trial percentages should not be treated as direct head-to-head evidence.
TRIUMPH-2 Also Had a Glycemic Objective
Weight loss was only part of the story in TRIUMPH-2.
Participants entered with an average A1C of approximately 7.7%.
Reported A1C changes at week 80 were:
| Group | A1C Change |
|---|---|
| 4 mg | -1.4 percentage points |
| 9 mg | -1.6 points |
| 12 mg | -1.5 points |
| Placebo | -0.2 points |
So TRIUMPH-2 provides evidence about both obesity and glycemic control in a population where the drug would have to address both problems simultaneously.
That is fundamentally different from the objective of TRIUMPH-1.
TRIUMPH-3: Severe Obesity Plus Cardiovascular Disease
TRIUMPH-3 pushed into an even higher-risk group.
Participants had a BMI of at least 35 kg/m² and established cardiovascular disease.
The study randomized roughly 1,950 participants to 9 mg, 12 mg, or placebo.
At week 80:
| Group | Average Weight Change |
|---|---|
| 9 mg | -21.6% |
| 12 mg | -22.6% |
| Placebo | -3.2% |
The average starting BMI was approximately 40.4 kg/m² and average body weight was 111.4 kg.
Again, the result was lower than TRIUMPH-1 and TRIUMPH-4 but somewhat higher than TRIUMPH-2 at the top dose.
The important point is that TRIUMPH-3 was not a healthy uncomplicated obesity cohort.
These participants already had established cardiovascular disease.
Did TRIUMPH-3 Prove Cardiovascular Benefit?
No.
TRIUMPH-3 did collect major cardiovascular event data, but the event counts were lower than anticipated.
In the prespecified in-study analysis, pooled retatrutide groups had a MACE-5 hazard ratio of 0.82 with a 95% confidence interval from 0.55 to 1.22.
For MACE-3, the hazard ratio was 1.12 with a 95% confidence interval from 0.64 to 1.96.
Both confidence intervals cross 1.0.
So these data do not establish either a cardiovascular benefit or a cardiovascular harm.
That question belongs to the much larger TRIUMPH-Outcomes trial, which is designed around cardiovascular and kidney events rather than weight loss.
TRIUMPH-4: Knee Osteoarthritis Changes the Primary Question
TRIUMPH-4 was different again.
Its 445 participants had obesity or overweight plus clinically and radiographically defined knee osteoarthritis. They did not have diabetes.
The study evaluated 9 mg and 12 mg retatrutide versus placebo for 68 weeks.
Weight change was:
| Group | Weight Change |
|---|---|
| 9 mg | -26.4% |
| 12 mg | -28.7% |
| Placebo | -2.1% |
That makes the 12 mg result numerically the largest of the four main Phase 3 TRIUMPH readouts so far, despite the trial being shorter than TRIUMPH-1.
But TRIUMPH-4 was not designed as a competition to see which trial could produce the highest weight-loss number.
It had a second co-primary endpoint: knee pain.
Knee Pain Fell Along With Body Weight
Participants began with an average WOMAC pain score of about 6.0 on the study’s normalized scale.
At week 68, average absolute changes were:
| Group | WOMAC Pain Change |
|---|---|
| Retatrutide 9 mg | -4.5 points |
| Retatrutide 12 mg | -4.4 points |
| Placebo | -2.4 points |
The corresponding reported percentage reductions were about 75.8%, 74.3%, and 40.3%, although those percentage calculations were post-hoc rather than prespecified endpoints.
Physical-function scores also improved substantially.
This makes TRIUMPH-4 important for a reason beyond weight loss: it tests whether treating obesity can alter a major mechanical and functional complication associated with excess body weight.
Why Was Weight Loss Lower in TRIUMPH-2?
This is one of the most obvious questions when the four studies are placed side by side.
The answer is that the trial does not isolate a single cause.
TRIUMPH-2 participants had type 2 diabetes. TRIUMPH-1 and TRIUMPH-4 excluded it. TRIUMPH-3 allowed participants with or without diabetes but required both severe obesity and established cardiovascular disease.
These are not interchangeable populations.
Different baseline disease states can affect food intake, metabolism, medication use, treatment adherence, and the amount of weight a participant can reasonably lose during a fixed period.
So it is reasonable to say:
Retatrutide produced less average weight reduction in the TRIUMPH-2 diabetes population than in the non-diabetes TRIUMPH-1 population.
It is not reasonable to infer from those two trials alone exactly why the difference occurred.
Why TRIUMPH-4 Should Not Be Called “Better” Than TRIUMPH-1
TRIUMPH-4’s 28.7% result is numerically slightly above TRIUMPH-1’s 28.3%.
The difference is only 0.4 percentage points.
TRIUMPH-4 had just 445 participants, only two active doses, a knee osteoarthritis requirement, and a 68-week primary endpoint.
TRIUMPH-1 randomized 2,339 participants and measured the main endpoint at 80 weeks.
There was no randomization between the two trials.
So saying that retatrutide “worked better” in TRIUMPH-4 would go beyond the evidence.
The correct interpretation is simply that both non-diabetes Phase 3 populations produced average weight reductions approaching 30% at the highest tested dose under the efficacy estimand.
Efficacy Estimand vs. Treatment-Regimen Estimand
Another important detail is hidden behind the numbers.
Most headline results discussed here use an efficacy estimand.
Conceptually, that estimates treatment efficacy under a framework in which participants remain on assigned treatment, with defined handling of intercurrent events.
Lilly also reports a treatment-regimen estimand, which is closer to asking what happened across randomized participants regardless of treatment adherence or certain subsequent interventions.
The difference can be meaningful.
For example, in TRIUMPH-1 at 12 mg:
Efficacy estimand: -28.3%
Treatment-regimen estimand: -25.0%.
Both numbers are legitimate, but they answer slightly different statistical questions.
That is another reason to check which estimand is being quoted before comparing trial results.
The Dose-Response Pattern Is Not Identical Across Trials
TRIUMPH-1 showed a clear increase from 4 mg to 9 mg and then a smaller additional increase at 12 mg.
TRIUMPH-2 showed a similar pattern, with a large difference between 4 mg and 9 mg but only a modest difference between 9 mg and 12 mg.
TRIUMPH-3 showed only a one-percentage-point difference between 9 mg and 12 mg.
TRIUMPH-4 showed a 2.3-point difference.
This does not establish that 12 mg is universally “better” or that 9 mg is equivalent.
Safety and tolerability also change with dose, and the trials were not designed to define one universal dose-response curve across all populations.
Tolerability Also Belongs in the Comparison
The weight-loss percentages are only half of the benefit-risk equation.
Across the TRIUMPH studies, gastrointestinal adverse events such as nausea, diarrhea, constipation, and vomiting were common.
In TRIUMPH-1, discontinuation because of adverse events increased from 4.1% at 4 mg to 11.3% at 12 mg, compared with 4.9% for placebo.
In TRIUMPH-2, adverse-event discontinuation was 3.8%, 11.6%, and 7.7% across 4, 9, and 12 mg, versus 4.9% with placebo.
In TRIUMPH-3, the corresponding rates were 9.8% with 9 mg and 13.5% with 12 mg, versus 4.8% with placebo.
So a higher dose cannot be evaluated only by looking at the additional percentage of body weight lost.
What Do TRIUMPH-1 Through TRIUMPH-4 Collectively Tell Us?
Taken together, the Phase 3 program shows that retatrutide can produce substantial body-weight reduction across several very different populations.
The strongest average weight reductions so far have occurred in the non-diabetes TRIUMPH-1 and TRIUMPH-4 populations.
Substantial but lower reductions were reported in type 2 diabetes and severe cardiovascular disease populations.
The trials also show that retatrutide’s development strategy is increasingly focused on obesity complications, not weight alone.
TRIUMPH-1 included obstructive sleep apnea and osteoarthritis basket studies.
TRIUMPH-3 studied people already living with cardiovascular disease.
TRIUMPH-4 made knee pain a co-primary endpoint.
The next generation of trials extends this idea further into long-term weight maintenance, chronic low back pain, cardiovascular outcomes, kidney disease, and head-to-head comparisons.
What the Four Trials Still Cannot Tell Us
These trials cannot tell us whether retatrutide is superior to tirzepatide.
That question requires TRIUMPH-5.
They cannot prove that retatrutide prevents heart attacks, strokes, heart failure, or kidney failure.
That requires TRIUMPH-Outcomes.
And they cannot tell us whether the impressive headline efficacy results will translate into the same outcomes in routine clinical practice if retatrutide is eventually approved.
Clinical trials operate under structured protocols, follow-up schedules, eligibility criteria, and treatment-monitoring systems that differ from ordinary care.
Publication Status Is Still Important
There is also an evidence-quality issue worth keeping visible.
The TRIUMPH trial program itself has a peer-reviewed design publication.
But as of September 4, 2026, the major efficacy results from TRIUMPH-1 through TRIUMPH-4 have not all appeared as full peer-reviewed outcomes manuscripts.
TRIUMPH-1 has been presented in detail at a major scientific meeting.
TRIUMPH-2 and TRIUMPH-3 were announced as topline Phase 3 findings in July 2026, with Lilly stating that detailed results would follow at medical meetings and in peer-reviewed journals.
TRIUMPH-4 likewise remains primarily available through Lilly’s Phase 3 reporting.
That means these are important Phase 3 data, but this article should be updated when complete manuscripts become available.
Conclusion
There is no single “retatrutide Phase 3 result.”
TRIUMPH-1 through TRIUMPH-4 studied four different clinical situations.
TRIUMPH-1 established the strongest broad obesity result, with average weight loss reaching 28.3% at 12 mg after 80 weeks.
TRIUMPH-2 showed substantial weight and A1C reductions in people with type 2 diabetes, with weight loss reaching 20.8%.
TRIUMPH-3 showed 22.6% average weight reduction in people with severe obesity and established cardiovascular disease.
TRIUMPH-4 combined 28.7% average weight reduction with large improvements in knee osteoarthritis pain.
Those results are impressive, but they should not be ranked as though they came from one head-to-head experiment.
Population, disease status, duration, dose, endpoints, statistical estimand, and tolerability all matter.
The next major step will be direct comparative and outcome evidence.
TRIUMPH-5 will compare retatrutide with tirzepatide. TRIUMPH-Outcomes will test whether the metabolic improvements translate into fewer major cardiovascular and kidney events.
Until then, the best reading of the Phase 3 evidence is not that one percentage defines retatrutide.
It is that triple GIP, GLP-1, and glucagon receptor agonism has now produced substantial effects across several distinct obesity-related disease populations, with important questions still being answered.
Retatrutide remains investigational and has not yet been approved by a regulatory agency.
References
Eli Lilly and Company. TRIUMPH-1 Phase 3 results. May 2026. Read the TRIUMPH-1 results
Eli Lilly and Company. TRIUMPH-2 and TRIUMPH-3 Phase 3 results. July 2026. Read the TRIUMPH-2 and TRIUMPH-3 results
Eli Lilly and Company. TRIUMPH-4 Phase 3 results. December 2025. Read the TRIUMPH-4 results
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, Obesity and Metabolism. View on PubMed
ClinicalTrials.gov. TRIUMPH-5: Retatrutide Compared With Tirzepatide, NCT06662383. View TRIUMPH-5
ClinicalTrials.gov. TRIUMPH-Outcomes, NCT06383390. View TRIUMPH-Outcomes