JGH Open published a narrative review on 4 September 2026 by Jasmine Gill and Priya Sumithran, from Alfred Health and Monash University in Melbourne, surveying how obesity medications have developed.
It opens with the part of the story that usually gets left out. Historically, the authors write, many obesity medications have been withdrawn from the market because of safety concerns.
That history is the reason the current numbers deserve more than a headline.
A framing note. These are approved medicines and this is a review of clinical evidence. Peptra Labs supplies Tirzepatide as a reference material for laboratory research only, and nothing below is guidance about human use or about weight loss.
What the review reports about tirzepatide
The authors describe the current generation of injectable incretin analogues, naming semaglutide and tirzepatide, as producing mean weight loss in the range of 15 to 20 percent over approximately 12 to 18 months.
They attribute the change to expanded scientific understanding of the mechanisms regulating appetite and energy balance, which they say has led to medications with greater safety and efficacy than their predecessors.
Beyond weight, they list additional substantial cardiometabolic benefits: reductions in adverse cardiovascular and kidney outcomes, and improvements in glycaemia, blood pressure, lipid profile and steatohepatitis.
Their conclusion is that as therapeutic options continue to expand, these medications are poised to play a critical role in the management of cardiometabolic disease.
Where the tirzepatide list needs a footnote
Four of the five items on the benefit list are things we have written about in the last two weeks, and the picture underneath each is more complicated than a list conveys.
| Claim in the review | What we covered |
|---|---|
| Reductions in adverse cardiovascular outcomes | a trial that met non-inferiority and missed superiority at P equals 0.09 |
| Reductions in adverse kidney outcomes | a database comparison with a mortality hazard ratio large enough to suggest confounding |
| Improvements in blood pressure | a comparison where blood pressure fell no more than with the guideline drug |
| Improvements in steatohepatitis | a phase 3 subgroup where the fibrosis endpoint did not separate |
None of that makes the review wrong. A narrative review summarises the direction of a literature, and the direction is genuinely favourable.
It does mean that the summary and the primary sources are two different reading experiences. A systematic review that placed the numbers side by side in Annals of Internal Medicine last week stated that heterogeneity prevented pooling, which is the caveat that disappears when a benefit becomes a bullet point.
Yesterday we covered a comparison in resistant hypertension where the blood pressure reduction was slightly smaller than with the comparator, not larger, and before that an earlier analysis of blood pressure in this class. Both statements can appear in the same literature because they measure different things, and only the primary papers say which.
The withdrawal history the review starts from
The historical framing is the most useful part of the piece for anyone assessing a compound today.
Obesity pharmacology has a long record of agents that reached the market and were removed after harms emerged, sometimes years later. The authors do not itemise them in the abstract, and the pattern is well known: efficacy established first, cardiovascular or psychiatric harm found afterwards, withdrawal follows.
What the authors argue is different this time is mechanistic understanding. The incretin pathway was characterised before tirzepatide and its class were designed against it, rather than a compound being found to work and the reason being reconstructed later.
That is a reasonable argument and it is not a guarantee. The mechanism being understood does not mean every downstream consequence is known, which is why post-marketing surveillance keeps producing the reports we have covered all week.
The disclosure on the tirzepatide review
The competing interests statement is specific and belongs in any summary of this review.
Sumithran has received payment, made to her institution, for speaking and advisory activities from Eli Lilly and Novo Nordisk, and has co-authored manuscripts with a medical writer funded by Eli Lilly. Gill declares nothing.
Those are the two companies that manufacture semaglutide and tirzepatide.
This is normal in the field and it is disclosed properly. It is also a favourable narrative review of two products, written in part by someone with a paid advisory relationship with both manufacturers, and a reader is entitled to weigh that while reading the conclusions.
Narrative reviews have no protocol, no prespecified inclusion criteria and no way for a reader to check what was left out, which is what makes the disclosure matter more here than it would in a systematic review.
Where the tirzepatide numbers actually come from
The 15 to 20 percent figure is a summary of trial results, and trials are the best evidence available for this question.
It is also worth remembering what the tirzepatide and semaglutide numbers describe: mean weight loss at 12 to 18 months, on treatment. We covered an estimate of how fast weight returns after stopping that put monthly regain at 1.04 kg, with half the loss projected to return within about seven and a half months.
Neither figure contradicts the other. Together they describe a treatment effect that is real while it is being given, which is a more complete sentence than either half.
What it means for the catalogue
A narrative review is a map of a field rather than a result, and the useful thing for a laboratory is what the map leaves out.
Retatrutide is not named alongside tirzepatide among the current generation here, because the review is describing agents in clinical use. Compounds still in trials appear in reviews as emerging options and then disappear again if the programme stops, which is the fate of most of them.
The historical point in the review is the one worth carrying: obesity pharmacology has withdrawn more agents than it has kept. Anyone working with tirzepatide or a compound in its class is working on a molecule whose full record is not written yet, and that is true of approved medicines as much as of research material.
For laboratories, our European research buyer guide covers procurement and documentation, everything is supplied on a research use only basis, and our ranking of the most-studied research peptides counts primary studies rather than reviews.
References
- Gill J, Sumithran P. The Evolution of Medications for Obesity Management. JGH Open, 4 September 2026, 10(9):e70466. doi 10.1002/jgh3.70466
- Moiz A, Filion KB, Samuels AE, et al. Efficacy and Safety of Glucagon-like Peptide-1 Receptor Agonists and Co-agonists for Weight Loss Among Adults Without Diabetes: An Updated Systematic Review. Annals of Internal Medicine, 1 September 2026
- Kow CS, Thiruchelvam K, Ramachandram DS, Zaihan AF. Weight Regain Trajectories After Discontinuation of Semaglutide or Tirzepatide. Endocrinology, Diabetes and Metabolism, September 2026, 9(5):e70325
- Tian Z, Willerding JM, Schmidt-Ott KM, Melk A, Schmidt BMW. Comparative effectiveness of GLP-1 receptor agonists versus mineralocorticoid receptor antagonists as fourth-line pharmacological therapy in patients with resistant hypertension. EClinicalMedicine, 29 August 2026, 99:104176
The products referenced on this site are supplied for laboratory research use only. They are not medicines and are not intended for human or veterinary use. This article summarises published research for informational purposes and is not medical advice. Statements about third-party studies belong to their authors.
