Retatrutide vs. Tirzepatide vs. Semaglutide: What the Latest Clinical Trials Actually Show
The Compound Edit | Peptides & Metabolic Research
Semaglutide changed the conversation about weight loss.
Then tirzepatide came along and raised expectations.
Now retatrutide is producing clinical trial results that have people asking an entirely new question:
How much further can obesity medicine actually go?
If you’ve followed the research, you’ve probably seen the numbers.
Nearly 15% weight loss.
More than 20%.
And now reports approaching 30%.
It’s easy to look at those percentages and assume we’ve found a clear winner.
But here’s what doesn’t always make it into the social media conversation.
Not all clinical trial percentages can be compared directly.
The participants may be different. The studies may run for different lengths of time. And researchers may use different statistical methods to calculate their results.
So rather than repeating everything we already know about GLP-1 receptors, let’s look at the actual evidence.
Which medications have been compared directly?
What do retatrutide’s newest results really mean?
And what should we be paying attention to beyond the number on the scale?
Let’s get into it.
First, a Quick Refresher
These medications influence overlapping but different metabolic pathways.
| Medication | Receptors activated | Regulatory status in the U.S. |
|---|---|---|
| Semaglutide | GLP-1 | Approved in specific products |
| Tirzepatide | GLP-1 and GIP | Approved in specific products |
| Retatrutide | GLP-1, GIP, and glucagon | Investigational |
We’ve already explored these receptor differences in our article about GLP-1, dual agonists, and triple agonists.
But understanding the mechanism is only the beginning.
The real question is what happens when researchers test these medications in people.
Semaglutide: The Trial That Helped Change Everything
In 2021, the STEP 1 trial helped establish just how effective GLP-1 receptor activation could be for weight management.
Researchers enrolled 1,961 adults with obesity or overweight without diabetes.
Participants received either semaglutide 2.4 mg or placebo alongside lifestyle intervention.
After 68 weeks, the average weight changes were:
- Semaglutide: -14.9%
- Placebo: -2.4%
For someone starting at 250 pounds, a 14.9% reduction would equal approximately 37 pounds.
These results were significant because they demonstrated that medication targeting a metabolic hormone pathway could produce substantial average weight loss.
And semaglutide’s research didn’t end with the scale.
Subsequent clinical studies have evaluated cardiovascular outcomes and other health effects in specific populations.
That broader evidence matters when comparing an established medication with one still undergoing clinical development.
Tirzepatide: What Happened When Researchers Targeted Two Receptors?
Tirzepatide was developed to activate both GLP-1 and GIP receptors.
Its SURMOUNT-1 trial evaluated adults with obesity or overweight without diabetes.
After 72 weeks, average weight reductions were approximately:
| Group | Average weight reduction |
|---|---|
| Tirzepatide 5 mg | 15.0% |
| Tirzepatide 10 mg | 19.5% |
| Tirzepatide 15 mg | 20.9% |
| Placebo | 3.1% |
These were substantial results.
But the more revealing comparison came later.
Because instead of comparing numbers from separate trials, researchers finally tested tirzepatide and semaglutide against one another.
The Head-to-Head Trial: Tirzepatide vs. Semaglutide
This is one of the most useful studies for understanding the difference between these medications.
In 2025, researchers published the SURMOUNT-5 trial.
The study included 751 adults with obesity without type 2 diabetes.
Participants were randomly assigned to receive tirzepatide or semaglutide, using the maximum tolerated doses specified by the trial.
After 72 weeks:
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| Medication | Average weight reduction |
|---|---|
| Tirzepatide | 20.2% |
| Semaglutide | 13.7% |
Tirzepatide also produced a greater average reduction in waist circumference.
The difference in average weight reduction was 6.5 percentage points.
And because both medications were studied in the same randomized trial, this comparison is much more meaningful than comparing two unrelated studies.
The result: Tirzepatide produced significantly greater average weight loss than semaglutide in this study.
But that doesn’t mean every individual will respond better to tirzepatide.
Clinical averages tell us about groups.
They don’t predict exactly how one person’s body will respond.
Now Let’s Talk About Retatrutide
Retatrutide is where the research becomes especially interesting.
Unlike semaglutide and tirzepatide, retatrutide activates three receptors: GLP-1, GIP, and glucagon.
Researchers are investigating whether that third pathway can produce additional metabolic effects.
And the 2026 Phase 3 findings have attracted enormous attention.
TRIUMPH-1: What the Published Study Actually Found
The TRIUMPH-1 trial enrolled 2,339 adults with obesity without diabetes.
Participants were randomly assigned to receive retatrutide or placebo for 80 weeks.
The study was published in The New England Journal of Medicine on September 29, 2026.
Here are the reported average weight changes using the trial’s primary treatment-regimen analysis:
| Group | Average weight change at 80 weeks |
|---|---|
| Retatrutide 4 mg | -17.6% |
| Retatrutide 9 mg | -23.7% |
| Retatrutide 12 mg | -25.0% |
| Placebo | -3.9% |
That’s an impressive result.
But you may have seen a different number circulating online.
28.3%.
So where did that come from?
Why Are Some Reports Saying 25% and Others Saying 28.3%?
This is exactly why understanding clinical research matters.
The 25.0% figure reflects the treatment-regimen analysis reported in the published study.
That approach accounts for participants according to their randomized treatment assignments, including treatment discontinuation and other events as specified in the analysis.
The 28.3% figure comes from an efficacy-oriented analysis reported by the manufacturer.
That analysis estimates treatment effects under different assumptions about treatment adherence and other events.
Neither number should be presented without explaining what it measures.
And they shouldn’t be treated as interchangeable.
When we compare clinical trial results, we need to ask:
Which population, which time point, and which statistical analysis produced this number?
Otherwise, we risk making one medication appear more effective simply because we’re comparing different types of results.
Does Retatrutide Beat Tirzepatide?
This is probably the question everyone wants answered.
And right now, the scientifically accurate answer is:
We don’t have enough direct comparative evidence to say that definitively.
Retatrutide’s TRIUMPH-1 results are extremely promising.
But comparing its 80-week results with tirzepatide’s 72-week SURMOUNT-1 results isn’t the same as running a head-to-head trial.
The populations, protocols, and analytical methods differ.
That means we cannot reliably calculate how much more weight someone would lose by choosing one over the other.
The SURMOUNT-5 trial gives us direct evidence that tirzepatide outperformed semaglutide in that study.
An equivalent published comparison establishing retatrutide’s superiority over tirzepatide is not yet available.
And that distinction matters.
Weight Loss Isn’t the Only Outcome Worth Watching
When discussing these medications, almost every headline focuses on percentages.
But obesity affects more than body weight.
Researchers also evaluate:
- Blood glucose and A1C.
- Waist circumference.
- Cardiovascular outcomes.
- Blood pressure.
- Sleep apnea.
- Joint pain and mobility.
- Treatment tolerability.
- Long-term safety and quality of life.
In TRIUMPH-1, retatrutide was also associated with improvements in knee osteoarthritis pain and obstructive sleep apnea measurements in relevant participant subgroups.
Those findings suggest researchers are looking beyond weight loss alone.
However, improvements in symptoms or risk factors aren’t automatically proof that a medication reduces heart attacks, strokes, or mortality.
Those outcomes require appropriately designed studies.
What About Side Effects?
This is where the comparison becomes more complicated.
All three medications can produce gastrointestinal adverse effects.
Commonly reported problems include nausea, vomiting, diarrhea, constipation, and abdominal discomfort.
In SURMOUNT-5, gastrointestinal events were the most common adverse events in both treatment groups, and most were mild to moderate.
Retatrutide’s Phase 3 study also reported gastrointestinal effects as the most common adverse events.
But it’s difficult to declare one medication the easiest to tolerate based on separate trials.
The dose-escalation protocols, populations, and methods of reporting may differ.
Approved semaglutide and tirzepatide products have established prescribing information describing important warnings and contraindications.
Retatrutide’s long-term safety profile is still being evaluated.
And greater average weight loss doesn’t automatically make a medication the best choice for every patient.
The Muscle-Loss Question Nobody Should Ignore
Let’s talk about something that deserves far more attention.
Body composition.
When someone loses a substantial amount of weight, some of that reduction can involve lean mass.
And lean mass isn’t exactly the same thing as muscle.
It also includes other tissues and water.
That’s why interpreting body-composition studies requires care.
For someone who has spent years building muscle, losing weight without considering muscle preservation can be frustrating.
Resistance training and adequate protein intake are important tools for supporting muscle during weight loss.
But researchers still need more detailed evidence about long-term muscle quality, strength, and physical function across different weight-loss medications.
The goal shouldn’t simply be to lose the most weight possible.
It should be to improve health while preserving as much functional tissue as possible.
What Happens After Treatment Stops?
Another major question is whether weight loss can be maintained.
Studies involving semaglutide and tirzepatide have demonstrated that weight regain commonly occurs after treatment withdrawal.
This reflects the chronic biological processes involved in obesity.
For retatrutide, long-term maintenance and discontinuation outcomes remain important research questions.
A medication producing dramatic weight loss during a trial doesn’t automatically tell us what happens five years later.
And that’s one reason long-term clinical evidence matters so much.
Why FDA Approval Matters
As of October 2026, semaglutide and tirzepatide are available in FDA-approved products for specific indications.
Retatrutide remains investigational.
That means it has not completed the regulatory process required for approved clinical use.
The research results are promising, but promising isn’t the same thing as approved.
Products marketed online as retatrutide aren’t equivalent to the investigational medication manufactured and monitored for clinical trials.
Questions about identity, purity, concentration, and safety remain significant.
So Which Medication Is Actually Best?
There’s no single answer that applies to everyone.
If we’re looking strictly at the strongest direct comparison between approved treatments, tirzepatide demonstrated greater average weight loss than semaglutide in SURMOUNT-5.
If we’re looking at emerging research, retatrutide has produced striking Phase 3 weight-loss results.
But the most appropriate treatment isn’t determined by one percentage.
It depends on medical history, treatment goals, approved indications, contraindications, side effects, and the strength of the available evidence.
And sometimes the medication with the largest average weight reduction isn’t the one that makes the most sense for a particular patient.
The Compound Edit Takeaway
The latest clinical trials tell us something important.
Semaglutide helped establish a new era of obesity treatment.
Tirzepatide demonstrated greater average weight loss than semaglutide in a direct randomized comparison.
And retatrutide’s Phase 3 results suggest that targeting three hormone receptors may produce substantial additional possibilities for metabolic medicine.
But comparing these treatments responsibly requires more than lining up three percentages.
We have to consider how the studies were designed, which patients participated, what outcomes were measured, and what researchers still don’t know.
The most exciting part isn’t deciding which medication has won.
It’s watching the science become more sophisticated.
Because the future of obesity treatment may involve more than losing weight.
It may involve preserving muscle, improving metabolic health, reducing complications, and finding approaches that work for different people.
And that’s the research worth paying attention to.
Keep Exploring on The Compound Edit
Want to understand the science behind these medications? Start with these previously published articles:
- GLP-1, GLP-2, GLP-3: What People Really Mean by Semaglutide, Tirzepatide & Retatrutide
- Retatrutide Isn’t Approved Yet. So Why Is Everyone Already Talking About It?
- Why Does Retatrutide Feel Like It Stopped Working?
- From 175 to 115: What My Retatrutide Journey Actually Looked Like
Continue Exploring
The Compound Edit is dedicated to exploring the science, research, and real conversations surrounding peptides, hormones, metabolism, performance, and longevity.
The Compound Edit is affiliated with Chuk BioWorks. While the two share an ownership connection, our editorial goal is to explore scientific research with transparency, including limitations, uncertainties, and potential risks.
Research & Sources
- Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine. 2021. https://doi.org/10.1056/NEJMoa2032183
- Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine. 2022. https://doi.org/10.1056/NEJMoa2206038
- Aronne LJ, et al. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity. New England Journal of Medicine. 2025. https://doi.org/10.1056/NEJMoa2416394
- Jastreboff AM, et al. Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity. New England Journal of Medicine. September 29, 2026. https://doi.org/10.1056/NEJMoa2604169
- Eli Lilly and Company. Q2 2026 Investor Presentation: TRIUMPH Trial Results. https://investor.lilly.com/static-files/ab69001c-650b-44f6-b629-309ee33f2335
Medical Disclaimer
The content published on The Compound Edit is intended for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment.
Medication selection and treatment decisions depend on individual medical circumstances. Retatrutide remains investigational and is not FDA-approved as of this article’s publication. Clinical trial findings are not instructions for personal use.
Stay curious. Keep learning. Continue exploring.
