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Hitting a Plateau on a GLP-1: What the Trials Actually Show

A plateau is what the published weight curves do. STEP 5 ran two years and landed at −15.2%; SURMOUNT-4 showed that continuing treatment past the flattening point kept and slightly extended the loss, while stopping reversed it. Four questions have randomized answers — escalate the dose, switch drugs, add a second mechanism, or continue as you are — and none of them is answered by a compounded peptide.

By Grant Delaney, Research Editor
Compounds

5

RCT evidence

3

FDA-approved

2

Weak evidence

1

Ranked by evidence

What actually has evidence behind it

Ordered by how far the published human evidence goes — strongest first. Availability is a separate question from evidence, so it is labeled separately.

  1. Tirzepatide (Zepbound, Mounjaro)

    FDA-approved
    Randomized trials

    Evidence strength: Randomized trials. Randomized controlled trials in humans, at scale.

    What it is

    A weekly GIP and GLP-1 receptor agonist. It has the two trials that speak most directly to a plateau: one on continuing, one on switching.

    What the evidence shows

    SURMOUNT-4 gave 783 adults open-label tirzepatide at the maximum tolerated dose of 10 or 15 mg for 36 weeks, by which point mean weight reduction was 20.9%. It then randomized 670 of them to continue or switch to placebo for 52 more weeks. From week 36 to week 88, weight changed −5.5% on continued tirzepatide against +14.0% on placebo, and 89.5% of the continued group kept at least 80% of the lead-in loss versus 16.6% on placebo. Total reduction from week 0 to 88 was 25.3% versus 9.9%. SURMOUNT-5 then randomized 751 adults with obesity head to head: −20.2% on tirzepatide against −13.7% on semaglutide at week 72, with waist circumference down 18.4 cm versus 13.0 cm.5,6

    The catch

    SURMOUNT-4's continued group still gained a further 5.5% loss over 52 weeks — real, but a fraction of the first 36 weeks. The flattening is not abolished by continuing; it is held. And SURMOUNT-5 enrolled people starting treatment, not people who had already plateaued on semaglutide, so it does not directly answer whether switching after a plateau reproduces that gap.

    Approved for this use and available by prescription.

  2. Semaglutide (Wegovy, Ozempic)

    FDA-approved
    Randomized trials

    Evidence strength: Randomized trials. Randomized controlled trials in humans, at scale.

    What it is

    A weekly GLP-1 receptor agonist, and the drug with both the longest published curve and the highest tested dose.

    What the evidence shows

    STEP 1 ran 1,961 adults for 68 weeks to a mean −14.9% against −2.4% on placebo. STEP 5 extended the question to two years in 304 adults: −15.2% at week 104 against −2.6%, with 77.1% losing at least 5%. The trial extension of STEP 1 measured the other direction — a year after stopping, participants had regained 11.6 of the percentage points lost, turning a 17.3% loss into 5.6%. On dose escalation, the STEP UP trial randomized 1,407 adults to semaglutide 7.2 mg, 2.4 mg or placebo for 72 weeks: −18.7% on 7.2 mg against −15.6% on 2.4 mg and −3.9% on placebo, a treatment difference of 3.1 percentage points.1,2,3,4

    The catch

    Two years of treatment produced 15.2% and one year of treatment produced 14.9% — most of the loss happens early, and the second year is largely maintenance. The higher dose bought 3.1 percentage points more, which is a real but modest return, and dose escalation is a prescriber's decision made against side effects, not a number to act on from a web page.

    Approved for this use and available by prescription.

  3. Cagrilintide + semaglutide (CagriSema)

    Research use only
    Randomized trials

    Evidence strength: Randomized trials. Randomized controlled trials in humans, at scale.

    What it is

    An amylin analog combined with semaglutide — a second satiety mechanism added to the one already in use, in a single weekly injection.

    What the evidence shows

    REDEFINE 1 randomized 3,417 adults: mean weight change at week 68 was −20.4% on the combination against −3.0% on placebo, a difference of 17.3 percentage points, with separate arms for semaglutide alone (302 participants) and cagrilintide alone (302). Gastrointestinal adverse events affected 79.6% of the combination group against 39.9% on placebo, mainly transient and mild to moderate.7,8

    The catch

    It is not approved, so there is no prescription route to it. The trial also enrolled people starting treatment rather than people already plateaued, so the 20.4% is not a measurement of what adding amylin does to a stalled curve. Cagrilintide alone performed well below the combination — the amylin half is not a cheaper version of this result.

    Sold for laboratory use. Not a legal medicine for people.

  4. Retatrutide

    Research use only
    Early human

    Evidence strength: Early human. Small, open-label, or phase 1/2 trials. Promising, unproven.

    What it is

    A triple agonist at the GIP, GLP-1 and glucagon receptors, still investigational. As of August 2026, a ClinicalTrials.gov intervention search for retatrutide returns 33 studies, 14 of them phase 3.

    What the evidence shows

    A phase 2 trial in 338 adults reported a mean −24.2% at 48 weeks on the 12 mg dose against −2.1% on placebo. A phase 3 trial has since published: TRANSCEND-T2D-1 ran 40 weeks in 537 adults with type 2 diabetes and reported a mean −15.3% on 12 mg against −2.6% on placebo.9,11

    The catch

    Neither trial enrolled people who had already stalled on another drug, so neither measures what this page is about. Both started participants from a baseline, which is a different question from restarting a curve that has flattened. The longer reads are still pending — as of August 2026 none of the four TRIUMPH registrational trials, which completed between November 2025 and June 2026, has posted results on ClinicalTrials.gov, and the latest weight timepoint in any retatrutide trial report indexed in PubMed is 48 weeks — less than the two years STEP 5 ran. It is also not approved, so nothing sold today under that name came from the company running those trials. Waiting for it is a strategy; sourcing it is not one this site will help with.

    Sold for laboratory use. Not a legal medicine for people.

  5. CJC-1295, ipamorelin and AOD-9604

    Compounding restricted
    Animal only

    Evidence strength: Animal only. Rodent or cell studies. Nothing published in humans.

    What it is

    Growth-hormone peptides, commonly offered as a 'stall-breaker' add-on when a GLP-1 curve flattens.

    What the evidence shows

    A 2026 orthopaedic review groups these as secretagogues acting through IGF-1 signalling and states that clinical trials are currently lacking across the compounds it covers.10

    The catch

    The 2025 network meta-analysis that mapped this field identified 56 randomized trials across six obesity medications — orlistat, semaglutide, liraglutide, tirzepatide, naltrexone/bupropion and phentermine/topiramate — enrolling 60,307 patients. No compounded peptide appears among the six. As of August 2026, a ClinicalTrials.gov intervention search returns three studies for ipamorelin, one for CJC-1295 terminated in 2006, and zero for AOD-9604 — none of them in people whose weight loss had stalled on another drug.

    Under active FDA restriction — compliant pharmacies decline to sell it.

The plateau is in the trial data

Nothing has gone wrong. Look at the published curves: STEP 5 reached −15.2% at two years, against −14.9% at 68 weeks in STEP 1 3. Almost all of the loss arrives in the first year, and the second year holds it.

SURMOUNT-4 tested the flattening directly. After a 36-week lead-in that produced 20.9% loss, participants who continued lost a further 5.5% over the next 52 weeks, while those switched to placebo gained 14.0% 5. Continuing does not restart the descent; it defends the position, and it turns out defending the position is most of the value.

The four things that have randomized answers

**Continue.** 89.5% of the continued arm in SURMOUNT-4 kept at least 80% of their lead-in loss, against 16.6% on placebo 5.

**Escalate.** STEP UP took semaglutide to 7.2 mg against 2.4 mg over 72 weeks: −18.7% versus −15.6%, a 3.1-point difference 4.

**Switch.** SURMOUNT-5 put tirzepatide against semaglutide head to head in 751 adults — −20.2% versus −13.7% at week 72 6. Read the caveat below before treating that as a switching result.

**Add a mechanism.** REDEFINE 1 paired an amylin analog with semaglutide and reached −20.4% at week 68 in 3,417 adults 7.

The caveat that applies to three of the four

SURMOUNT-5, STEP UP and REDEFINE 1 all enrolled people starting or continuing treatment — not people who had specifically plateaued on a different drug and then switched. Their numbers describe what those regimens achieve from where their participants began.

That is a meaningful gap, and it is the reason a prescriber's judgement matters more here than a table of percentages. What the data does support is that the choices exist and have been quantified, which is more than can be said for the alternatives below.

What gets sold into a stall

A flattening curve is a good moment to sell someone something, and the products aimed at it are growth-hormone peptides. The 2025 network meta-analysis that pooled 56 randomized trials and 60,307 patients covers six medications; none of them is a compounded peptide 8. Our weight-loss page covers the same compounds against the primary outcome, and the muscle-loss page covers what the loss is made of.

Questions

Frequently asked questions

Why has my weight loss stopped on a GLP-1?

Because that is the shape of the published curve. STEP 1 reached −14.9% at 68 weeks and STEP 5 reached −15.2% at 104 weeks — the second year is mostly maintenance. In SURMOUNT-4, participants who continued tirzepatide past a 36-week 20.9% loss lost a further 5.5% over the next 52 weeks, while those switched to placebo gained 14.0%.

Does a higher dose break a plateau?

STEP UP randomized 1,407 adults to semaglutide 7.2 mg, 2.4 mg or placebo for 72 weeks and reported −18.7%, −15.6% and −3.9%. That is a 3.1-percentage-point advantage for the higher dose. Those are the doses the trial administered; whether escalation is appropriate for you is a decision for your prescriber, made against side effects.

Should I switch from semaglutide to tirzepatide?

SURMOUNT-5 compared them head to head in 751 adults and found −20.2% on tirzepatide against −13.7% on semaglutide at week 72. The caveat matters: participants were beginning that treatment, not switching after a plateau, so the trial does not directly measure the switch you would be making.

Will adding a peptide restart the loss?

No randomized trial has tested that. The combination with randomized evidence is cagrilintide plus semaglutide, which reached −20.4% at week 68 in 3,417 adults and is not approved. The 2025 network meta-analysis of 56 trials and 60,307 patients covers six obesity medications, none of them a compounded peptide, and as of August 2026 the registry footprint for ipamorelin, CJC-1295 and AOD-9604 contains no trial in people whose loss had stalled.

Keep reading

Go deeper on one compound

Tirzepatide

Full trial-by-trial evidence review.

Semaglutide

Full trial-by-trial evidence review.

Retatrutide

Full trial-by-trial evidence review.

Retatrutide vs. Tirzepatide: What the Trials Actually Found

Two trial programs, compared side by side — not head to head.

Reconstitution calculator

Converts a dose you've chosen into syringe units. Recommends nothing.

Retatrutide calculator

Converts a dose you've chosen into syringe units. Recommends nothing.

Sources

References

  1. Wilding JPH, Batterham RL, Calanna S, et al. (2021). Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine. https://pubmed.ncbi.nlm.nih.gov/33567185/
  2. Wilding JPH, Batterham RL, Davies M, et al. (2022). Weight regain and cardiometabolic effects after withdrawal of semaglutide: The STEP 1 trial extension. Diabetes, Obesity and Metabolism. https://pubmed.ncbi.nlm.nih.gov/35441470/
  3. Garvey WT, Batterham RL, Bhatta M, et al. (2022). Two-year effects of semaglutide in adults with overweight or obesity: the STEP 5 trial. Nature Medicine. https://pubmed.ncbi.nlm.nih.gov/36216945/
  4. Wharton S, Freitas P, Hjelmesæth J, et al. (2025). Once-weekly semaglutide 7·2 mg in adults with obesity (STEP UP): a randomised, controlled, phase 3b trial. Lancet Diabetes & Endocrinology. https://pubmed.ncbi.nlm.nih.gov/40961952/
  5. Aronne LJ, Sattar N, Horn DB, et al. (2024). Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial. JAMA. https://pubmed.ncbi.nlm.nih.gov/38078870/
  6. Aronne LJ, Horn DB, le Roux CW, et al. (2025). Tirzepatide as Compared with Semaglutide for the Treatment of Obesity. New England Journal of Medicine. https://pubmed.ncbi.nlm.nih.gov/40353578/
  7. Garvey WT, Blüher M, Osorto Contreras CK, et al. (2025). Coadministered Cagrilintide and Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine. https://pubmed.ncbi.nlm.nih.gov/40544433/
  8. McGowan B, Ciudin A, Baker JL, et al. (2025). A systematic review and meta-analysis of the efficacy and safety of pharmacological treatments for obesity in adults. Nature Medicine. https://pubmed.ncbi.nlm.nih.gov/41039116/
  9. Jastreboff AM, Kaplan LM, Frías JP, et al. (2023). Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. New England Journal of Medicine. https://pubmed.ncbi.nlm.nih.gov/37366315/
  10. Rahman OF, Lee SJ, Seeds WA (2026). Therapeutic Peptides in Orthopaedics: Applications, Challenges, and Future Directions. JAAOS Global Research & Reviews. https://pubmed.ncbi.nlm.nih.gov/41490200/
  11. Bajaj HS, Welch M, Shah P, et al. (2026). Efficacy and safety of retatrutide, a GIP, GLP-1, and glucagon receptor agonist, in people with type 2 diabetes and inadequate glycaemic control with diet and exercise (TRANSCEND-T2D-1): a double-blind, randomised, phase 3 trial. The Lancet. https://pubmed.ncbi.nlm.nih.gov/42250575/

Medical disclaimer: This content is for general educational purposes only and is not medical advice, diagnosis, or treatment. Always consult a licensed healthcare professional before starting, stopping, or changing any treatment.