Retatrutide Phase 3 Results: What TRIUMPH-2 Really Showed About Weight Loss, A1C & Metabolic Health

Retatrutide has been one of the most closely watched experimental metabolic drugs in development.

Now, the detailed Phase 3 TRIUMPH-2 results provide the clearest picture yet of how the drug performed in adults living with both type 2 diabetes and overweight or obesity.

The results attracted attention for one obvious reason:

The amount of weight loss was unusually large for a late-stage diabetes trial.

But the headline numbers only tell part of the story.

TRIUMPH-2 also reported meaningful changes in:

- A1C
- Waist circumference
- Triglycerides
- Non-HDL cholesterol
- Systolic blood pressure
- High-sensitivity C-reactive protein
- The percentage of participants reaching major weight-loss thresholds

The trial also provides important information about tolerability and adverse effects.

So what did the study actually show?

And what does it mean for the future of retatrutide?

What Is Retatrutide?

Retatrutide is an investigational once-weekly drug being developed by Eli Lilly.

It is designed to activate three hormone receptors:

- GIP
- GLP-1
- Glucagon

This is why retatrutide is often described as a triple hormone receptor agonist.

The three receptors influence different parts of energy balance and glucose metabolism.

GLP-1 receptor activation is associated with:

- Appetite regulation
- Glucose-dependent insulin secretion
- Reduced glucagon signaling in certain metabolic states
- Slower gastric emptying
- Satiety

GIP receptor signaling also plays a role in insulin secretion and metabolic regulation.

Glucagon receptor activity is especially interesting because glucagon can influence:

- Hepatic metabolism
- Energy expenditure
- Lipid metabolism
- Glucose regulation

Retatrutide attempts to combine these three biological pathways into a single molecule.

That makes it mechanistically different from medications that act on only one or two incretin-related receptors.

What Was TRIUMPH-2?

TRIUMPH-2 was a randomized Phase 3 clinical trial evaluating retatrutide in adults with:

type 2 diabetes plus obesity or overweight.

The study enrolled 1,152 participants.

Participants were assigned to receive:

- Retatrutide 4 mg
- Retatrutide 9 mg
- Retatrutide 12 mg
- Placebo

Treatment continued for 80 weeks.

The average starting body weight was approximately:

234.6 pounds

The average starting BMI was:

38.2 kg/m²

And the average starting A1C was:

7.7%

The study was designed to evaluate both weight reduction and metabolic outcomes.

The Headline Result: 20.8% Average Weight Loss

Using Lilly's efficacy estimand, participants receiving the highest studied dose of 12 mg retatrutide lost an average of:

20.8% of their starting body weight

That represented approximately:

49.6 pounds

over 80 weeks.

The other dose groups also showed substantial reductions.

4 mg Retatrutide

Average weight reduction:

12.7%

Approximately:

29.8 pounds

9 mg Retatrutide

Average weight reduction:

19.1%

Approximately:

45.4 pounds

12 mg Retatrutide

Average weight reduction:

20.8%

Approximately:

49.6 pounds

Placebo

Average weight reduction:

4.0%

Approximately:

9.3 pounds

These results are especially notable because people with type 2 diabetes have historically tended to lose less weight in obesity-drug trials than comparable populations without diabetes.

Where Did the 60-Pound Number Come From?

One of the most widely circulated headlines from TRIUMPH-2 was that participants lost around 60 pounds, or more than 23% of their body weight.

That result is real.

But it needs context.

It did not represent the average result for everyone receiving 12 mg.

Instead, Lilly reported that participants who entered the study with a baseline BMI of 35 or higher and received 12 mg lost an average of:

60.8 pounds

or:

23.4% of body weight

That was a subgroup result.

So the most accurate way to report the study is:

The overall 12 mg group lost an average of 20.8%, while participants starting with BMI ≥35 lost an average of 23.4%.

That distinction matters.

More Than Half Lost at Least 20%

Average weight loss is useful, but responder rates tell us how many individual participants crossed meaningful thresholds.

At the 12 mg dose:

- 67.0% lost at least 15% of their body weight
- 52.0% lost at least 20%
- 34.9% lost at least 25%

By comparison, in the placebo group:

- 6.4% lost at least 15%
- 1.5% lost at least 20%
- 0.8% lost at least 25%

This is one of the more striking parts of the study.

The 20.8% average was not driven only by a handful of extreme responders.

A substantial portion of the treatment group reached large weight-loss thresholds.

Nearly 60% No Longer Met BMI Criteria for Obesity

Another result received less attention but may be equally meaningful.

By the end of the study:

59.5% of participants receiving 12 mg no longer met BMI criteria for obesity.

That does not mean BMI alone determines metabolic health.

BMI has important limitations and does not measure body composition, visceral fat, or individual metabolic risk.

Still, it provides a useful way to understand the magnitude of the average weight change seen across the trial population.

A1C Also Fell Substantially

TRIUMPH-2 was not only an obesity trial.

Every participant also had type 2 diabetes.

The study therefore evaluated blood-glucose control using A1C.

Average A1C at baseline was approximately:

7.7%

At 80 weeks, A1C changed by approximately:

Retatrutide 4 mg

-1.4 percentage points

Retatrutide 9 mg

-1.6 percentage points

Retatrutide 12 mg

-1.5 percentage points

Placebo

-0.2 percentage points

That means participants were not only losing significant amounts of weight.

Many were also reaching substantially lower long-term blood-glucose levels.

Up to 40% Reached A1C Below 5.7%

One of the most eye-catching metabolic findings involved the percentage of participants reaching an A1C below 5.7%.

An A1C below 5.7% is generally considered within the normal laboratory range.

The percentage reaching that level was:

- 28.4% with 4 mg
- 40.0% with 9 mg
- 39.3% with 12 mg
- 4.4% with placebo

It is important to interpret this carefully.

Reaching an A1C below 5.7% while receiving medication does not necessarily mean diabetes has permanently disappeared.

But it does demonstrate the magnitude of glycemic improvement achieved during treatment.

Most Participants Reached A1C at or Below 6.5%

At week 80:

- 73.1% of the 4 mg group reached A1C ≤6.5%
- 79.2% of the 9 mg group reached A1C ≤6.5%
- 79.0% of the 12 mg group reached A1C ≤6.5%
- 26.3% of the placebo group reached that threshold

This reinforces one of the central themes of TRIUMPH-2:

Retatrutide appeared to affect both body weight and glucose control simultaneously.

The Study Also Looked Beyond Weight and A1C

The highest retatrutide dose was associated with improvements across several additional cardiometabolic measurements.

According to Lilly's detailed TRIUMPH-2 results, the 12 mg group showed average reductions of approximately:

- 39.5% in triglycerides
- 19.6% in non-HDL cholesterol
- 10.8 mmHg in systolic blood pressure
- 6.7 inches in waist circumference
- 58.3% in high-sensitivity C-reactive protein

These outcomes matter because obesity and type 2 diabetes rarely exist in isolation.

They are often accompanied by:

- Hypertension
- Abnormal lipids
- Visceral adiposity
- Chronic low-grade inflammation
- Cardiovascular risk

The trial therefore provides a broader picture of metabolic change than weight loss alone.

Why the hsCRP Result Is Interesting

High-sensitivity C-reactive protein, or hsCRP, is a commonly measured marker associated with systemic inflammation and cardiovascular risk.

The reported average reduction of 58.3% at the highest dose is notable.

However, inflammatory biomarkers need careful interpretation.

A reduction in hsCRP could result from several overlapping changes, including:

- Reduced body weight
- Less visceral fat
- Improved glucose control
- Improved lipid metabolism
- Direct or indirect changes in inflammatory signaling

The study does not establish that retatrutide should be considered an anti-inflammatory treatment.

But it adds another interesting signal to the broader relationship between metabolic improvement and inflammation.

Efficacy Estimand vs. Treatment-Regimen Estimand

One reason different articles may report slightly different TRIUMPH-2 weight-loss numbers is the use of different statistical approaches.

The widely reported:

20.8% average weight loss

comes from the efficacy estimand.

This approach estimates the treatment effect under assumptions that focus on what happens while participants remain on assigned therapy without certain intercurrent events affecting the analysis.

A more conservative treatment-regimen estimand includes the effects of discontinuation and other events that occur during the study.

Published reporting around the full dataset has placed the 12 mg result at approximately:

18.8% average weight loss

using that approach.

These numbers are not necessarily contradictory.

They answer slightly different questions.

This is why clinical-trial headlines should always be interpreted together with the statistical method behind them.

Why This Matters

The difference between 18.8% and 20.8% may appear small.

But it illustrates an important principle:

Clinical-trial results depend partly on how the data are analyzed.

An efficacy estimand asks something closer to:

How effective was the treatment under the trial's efficacy assumptions?

A treatment-regimen analysis asks something closer to:

What happened across the randomized group when treatment discontinuation and other real-world trial events are included?

Both can be scientifically useful.

Neither should be presented without context.

What Were the Main Side Effects?

The strongest efficacy results also came with gastrointestinal adverse effects.

At the 12 mg dose, Lilly reported:

- Diarrhea: 33.6%
- Nausea: 28.0%
- Constipation: 16.8%
- Decreased appetite: 17.1%
- Vomiting: 15.7%

These effects are broadly consistent with the gastrointestinal profile seen with other medications involving GLP-1 receptor activity.

Most were described as mild to moderate and generally resolved during treatment.

Dysesthesia Was Also Reported

Another adverse event worth noting was dysesthesia.

Dysesthesia refers to abnormal sensations such as:

- Tingling
- Burning
- Pins-and-needles
- Altered skin sensation

Reported rates were:

- 4.5% at 4 mg
- 5.6% at 9 mg
- 7.3% at 12 mg
- 0.7% with placebo

This is an important safety signal to continue watching in future retatrutide trials and regulatory review.

How Many Participants Stopped Treatment Because of Side Effects?

Discontinuation because of adverse events occurred in:

- 3.8% with 4 mg
- 11.6% with 9 mg
- 7.7% with 12 mg
- 4.9% with placebo

Interestingly, discontinuation was not perfectly dose-dependent.

The 9 mg group had a higher reported discontinuation rate than the 12 mg group.

That is another reminder that trial tolerability does not always follow a perfectly linear pattern.

Why Is Retatrutide Different From Current GLP-1 Drugs?

Retatrutide is frequently grouped into the broader GLP-1 conversation.

But describing it simply as a “GLP-1 drug” leaves out a major part of its mechanism.

Retatrutide activates:

GIP + GLP-1 + glucagon receptors

Current metabolic drugs use different combinations of these pathways.

Semaglutide primarily targets the GLP-1 receptor.

Tirzepatide activates GIP and GLP-1 receptors.

Retatrutide adds glucagon receptor activity to those two pathways.

Researchers are investigating whether that third receptor helps explain some of the larger weight-loss effects observed in clinical studies.

Is Retatrutide FDA-Approved?

No.

This is especially important because of the amount of attention the compound receives online.

Retatrutide remains investigational.

It has not yet been approved by the U.S. Food and Drug Administration.

Lilly currently says it plans to submit a Biologics License Application in Q1 2027.

Regulatory review would then determine whether the evidence supports approval, for which indications, and under what labeling and safety requirements.

Why the Phase 3 Results Matter

Phase 2 studies had already suggested that retatrutide could produce substantial weight loss.

Phase 3 matters because these larger late-stage trials are designed to provide the evidence regulators use when evaluating whether a drug should be approved.

TRIUMPH-2 also focuses on an especially important population:

people who have obesity or overweight and type 2 diabetes at the same time.

That combination is extremely common.

It is also a population in which achieving very large amounts of weight loss with medication has historically been challenging.

That makes the TRIUMPH-2 results particularly significant.

Does 23.4% Mean Everyone Can Expect That Result?

No.

Clinical-trial averages should never be interpreted as guaranteed individual outcomes.

The 23.4% figure applies to a subgroup of participants with baseline BMI ≥35 receiving the 12 mg dose.

Individual responses varied.

Some participants lost substantially more.

Others lost less.

Clinical outcomes can depend on many factors, including:

- Starting body weight
- Metabolic health
- Treatment adherence
- Side effects
- Dose tolerance
- Genetics
- Lifestyle
- Other medications
- Duration of treatment

The study reports averages across groups, not predictions for individual patients.

What TRIUMPH-2 Does Not Yet Tell Us

Despite the strength of the results, important questions remain.

The study does not yet establish:

- Long-term outcomes over many years
- What happens after treatment is stopped
- Long-term cardiovascular-event reduction
- Long-term kidney outcomes
- Comparative effectiveness against every existing obesity medication
- Real-world adherence outside clinical trials
- Commercial pricing
- Insurance access
- Final FDA labeling

Several additional retatrutide studies are designed to answer some of these questions.

The Bigger Retatrutide Program

TRIUMPH-2 is only one part of Lilly's larger retatrutide development program.

Other trials are studying the compound in populations involving:

- Obesity without diabetes
- Severe obesity
- Cardiovascular disease
- Knee osteoarthritis
- Obstructive sleep apnea
- Longer-term cardiovascular and kidney outcomes

That broader program will help determine whether the dramatic effects on body weight translate into meaningful improvements in long-term health outcomes.

Why Weight Loss Is Only Part of the Story

The biggest headline from TRIUMPH-2 will understandably be:

up to 20.8% average weight loss

and:

23.4% in the BMI ≥35 subgroup.

But focusing only on weight misses much of what makes the study interesting.

TRIUMPH-2 also reported changes in:

- Glycemic control
- Blood pressure
- Lipids
- Waist circumference
- Inflammatory markers
- Obesity classification

This reflects a broader change in obesity research.

Scientists are increasingly studying obesity treatment not only in terms of pounds lost, but also in terms of:

cardiometabolic health.

The Bottom Line

The full Phase 3 TRIUMPH-2 results establish retatrutide as one of the most significant investigational metabolic drugs currently in late-stage development.

In adults with type 2 diabetes and overweight or obesity, the 12 mg dose produced:

20.8% average weight loss using the efficacy estimand

or approximately:

49.6 pounds over 80 weeks.

Among participants starting with BMI ≥35:

23.4% average weight loss

or approximately:

60.8 pounds

was reported.

At the same time:

- 52% of participants receiving 12 mg lost at least 20%
- 34.9% lost at least 25%
- 59.5% no longer met BMI criteria for obesity
- A1C fell by up to 1.6 percentage points
- Up to 40% reached A1C below 5.7%
- Multiple cardiometabolic risk markers also improved

The results are impressive.

They are also still clinical-trial results for an investigational drug.

Retatrutide has not yet been FDA-approved, and long-term regulatory, safety, cardiovascular, access, and real-world questions remain.

The most accurate takeaway is not simply:

“Retatrutide makes people lose 60 pounds.”

It is:

TRIUMPH-2 shows that retatrutide produced substantial average weight loss together with major improvements in glycemic and cardiometabolic measures in a population where both obesity and type 2 diabetes are especially difficult to treat.

And that is why these Phase 3 results are receiving so much attention.

Sources & Further Reading

Eli Lilly and Company — Detailed TRIUMPH-2 Phase 3 Results

Lilly's September 2026 release includes the complete efficacy-estimand weight-loss, A1C, responder, cardiometabolic and adverse-event data discussed in this article.

Read Lilly's detailed TRIUMPH-2 results

TRIUMPH-2 Clinical Trial — NCT05929079

The clinical-trial record describes the Phase 3 design, population, enrollment and study endpoints.

View the TRIUMPH-2 trial information

European Association for the Study of Diabetes — TRIUMPH-2

The detailed results were presented at the 2026 EASD Annual Meeting and published simultaneously in The Lancet.

Read the EASD research summary

Eli Lilly — What to Know About Retatrutide

Lilly's current information page explains retatrutide's investigational status and broader clinical-development program.

Read Lilly's retatrutide overview

Educational and Research Use Only

This article is provided for educational purposes only.

Retatrutide remains investigational and is not currently FDA-approved.

This article does not provide medical advice and does not recommend purchasing, administering, compounding, or using retatrutide or any other investigational product.

Clinical-trial results describe outcomes observed in defined research populations and should not be interpreted as guaranteed individual results.

Medical decisions involving diabetes, obesity, weight management, or prescription medications should be discussed with a qualified healthcare professional.