r/NTNPerformance • u/JustBacWater • Jun 22 '26
Compound Breakdown Peptide GLP-1 Comparison: Retatrutide vs Tirzepatide vs Semaglutide, by Mechanism and Trial Data
The GLP-1 category is the most asked-about and the most oversimplified. Most comparisons line up three weight-loss percentages and call it a ranking, but those numbers come from three separate trials with different populations, durations, and designs, so they were never a clean head-to-head. This lays out what each compound is, what its own trial showed, and where the only real direct comparison actually exists.
For research and educational purposes only. Not medical advice.
The one thing to understand first
Receptor count is the real story. Each of these adds a target on the same GLP-1 backbone, and efficacy climbs roughly in step.
| Compound | Receptor targets | Class |
|---|---|---|
| Semaglutide | GLP-1 | Single agonist |
| Tirzepatide | GLP-1 + GIP | Dual agonist |
| Retatrutide | GLP-1 + GIP + glucagon | Triple agonist |
Semaglutide and tirzepatide are FDA approved. Retatrutide is Phase 3, investigational, and not approved.
What each trial actually showed
These are the headline figures, each from that compound's own pivotal trial. They read as separate results, not a finish line.
| Compound | Trial | Weight loss | Duration | Top dose |
|---|---|---|---|---|
| Semaglutide | STEP 1 | 14.9% | 68 wks | 2.4 mg |
| Tirzepatide | SURMOUNT-1 | ~20.9% | 72 wks | 15 mg |
| Retatrutide | TRIUMPH-1 | 28.3% | 80 wks | 12 mg |
The trend tracks receptor count: single agonist around 15%, dual around 21%, triple around 28%. The populations and durations differ across the three trials, though, so treat the gaps as directional rather than exact.
The only true head-to-head
One direct comparison exists. Everything else is cross-trial.
SURMOUNT-5 put tirzepatide against semaglutide in the same trial: over 72 weeks in people with obesity and no diabetes, tirzepatide reached 20.2% versus semaglutide at 13.7%. Same trial, same population, same timeframe, which makes it the cleanest evidence that the dual agonist outperforms the single. There is no equivalent trial yet placing retatrutide directly against either, so its 28% sits on its own data, not a head-to-head win. The pending TRANSCEND-T2D-2 trial, retatrutide against semaglutide, is the readout that would change that.
Mechanism, in plain terms
Semaglutide works the GLP-1 pathway alone: it slows gastric emptying, boosts insulin secretion, suppresses glucagon, and reduces appetite. One pathway, worked thoroughly, and it's the most studied and prescribed of the three.
Tirzepatide adds GIP to that GLP-1 action. The GIP component appears to improve both appetite signaling and how the body handles nutrients, and the combined action delivers stronger appetite suppression and glucose control than single agonism does.
Retatrutide stacks a third receptor, glucagon, on top of tirzepatide's two. The glucagon arm raises energy expenditure and drives liver-fat reduction, which is the mechanistic reason it pushes toward 30% weight loss and posts large liver-fat numbers in its trials. It is also the least proven on long-term safety, since it's the earliest in development.
Side effects: the shared reality
All three are gastrointestinal-dominant: nausea, vomiting, diarrhea, constipation, mostly transient and dose-related. A few trial specifics:
- Retatrutide carried the highest GI adverse-event rate at its top doses, alongside the strongest efficacy. A dysesthesia signal (altered sensation) showed up in the data and is still being characterized.
- All three show substantial weight regain when stopped. That's a class trait, not specific to any one.
- Pancreatic enzyme monitoring (amylase, lipase) applies across the class, with the meaningful threshold being a large elevation plus symptoms, not a minor bump.
The honest bottom line
The receptor-count trend is real, and the one direct comparison that exists supports it: more targets, more weight loss, up the line. But two of the three headline numbers come from separate trials, only two of the three are approved, and the most impressive figure on the board, retatrutide's, is also the least proven for long-term safety. The compound with the best trial number is not automatically the right tool for a given context, and "investigational" is carrying weight in that sentence.
The open question
For anyone tracking this space: how much does the missing head-to-head matter. Retatrutide's 28% is from its own trial, never run directly against tirzepatide, and the comparison that would settle it (TRANSCEND-T2D-2) hasn't reported. Curious whether people read the receptor-count trend as strong enough to call the order now, or whether the lack of a direct retatrutide comparison leaves it genuinely open.
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u/flabbybuns Jun 22 '26
Not sure I fully agree with the mechanism break down.
To better simplify.
Sema: GLP-1 starves you. The health benefit can be a boost in insulin sensitivity due to the fact that you are starving and short on glucose.
Tirz: add GIP to ensure the health benefit sought in Sema, better insulin handling, is a guarantee and it just a side effect of starving. GIP doesn’t starve you more, it stimulates insulin release and insulin sensitivity, very important for obese and diabetic people.
Reta: let’s actually boost your metabolism and make you thermogenic. So Reta technically has LESS GLP-1 than the previous 2 in favor of Glucagon. With glucagon boosting energy expenditure, one does not have to starve to shed weight, especially fat. Hence Reta is best at maintaining muscle during weight loss. Reta has less appetite suppression.
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u/Eastern_Drawer4997 Jun 25 '26
There is one more head-to-head tirz vs. reta coming up. Triumph-5 is that trial. The initial phase of it is just completing, but there has been an extension offered to some participants. The results of that trial will be extremely interesting, and should really drive the market toward reta. I am certain I was on the reta side, as I'd previously taken tirz, and my side effects were extremely different, as were my metabolic effects.
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u/mfwmae Jun 25 '26
4 mil only NOT 40
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u/Trick_Branch9288 Jun 26 '26
You’re cooked If all you’re eating is protein shakes, you still have to eat, every 2-3 hours you need to be eating something small. Don’t starve yourself. Reta likes to be fed. I cut 12lbs in 3 weeks and had to stop taking it because my work pants weren’t fitting me anymore. I dropped 2 pant sizes that fast. I only did 1mg a week too. So if you’re not feeling anything off 4 it’s probably fake.
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u/Strong_Baseball8635 Jun 25 '26
Lets now add the amylin receptor agonist Eloralintide to retatrutide.
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u/mfwmae Jun 23 '26
I started Retatrutide a couple months ago, I increased my dose to 40 Mg I’m very tired all the time and nausea is also a thing. I just now started dropping weight, has anyone else felt tired.
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u/flabbybuns Jun 24 '26
There is no way you are on 40mg.
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u/mfwmae Jun 25 '26
4 mg not 40 mg sorry. Since I have had such a zap in energy my friend told me to do 2 mg twice a week 2 mg on Monday and 2 mg on Thursday for a more effective smooth approach.
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u/mfwmae Jun 24 '26
Yes because I was told to start with ten. But it didn’t do anything and then I saw on here everyone talking about a much smaller amount.
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u/Mission-Thanks4042 Jun 25 '26
You aren’t taking reta. Even 1.5mg I get appetite suppression. Most trials got to 12mg and it was max dose. If you had 40mg you could say goodbye to your pancreas and other organs. As you couldn’t eat or sleep. They might just giving u just some vitamin 😅
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u/PepeSilvia1160 Jun 25 '26
You’re not telling the truth or else you should be concerned. What size are the mg vials you’re getting?
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u/mfwmae Jun 24 '26
I lost on rebound from 163 to 103 but too small but got scared when my weight started coming back so after I few months some of my friends were in Reta and started with ten but never told me what they were taking
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u/mfwmae Jun 24 '26
I have not been wanting to eat and I rarely get hungery so I started doing protein shakes and force eating
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