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On May 11, 2025, the study “Tirzepatide as Compared with Semaglutide for the Treatment of Ob*sity” was published in the New England Journal of Medicine.
This study was, essentially, a cage match between the two newest weight loss drugs to see which one created more weight loss. Their use of “the treatment of ob*sity” in the title is a weight loss industry marketing trick that I’ve written about previously. And if you’re thinking something like - wait, don’t these studies already exist? - you are basically right but we’ll get to that later.
First things first, I am still seeing a lot of confusion about these drugs, their uses, and their various brand names in the media, so I want to start with the very basics. These were originally type 2 diabetes drugs with a side effect of a bit of weight loss. The manufacturers then set out to see if high doses of the meds (in the case of Semaglutide, often higher than the maximum dose for Type 2 Diabetes) increased the side effect of weight loss. They did, and so the pharma companies sought, and received, FDA approval of these drugs as weight loss medications.
These drugs may have other actual health benefits besides type 2 diabetes management, but that would need to be proven directly, not inferred from any (short-term) weight loss.
Semaglutide
Manufacturer: Novo Nordisk
GLP-1 agonist
Ozempic - Brand name for Type 2 Diabetes, weekly injection
FDA Approved December, 2017
Rebylsus - Brand name for Type 2 Diabetes, daily pill
FDA Approved September, 2019
Wegovy - Brand name for Weight Loss, weekly injection
FDA Approved June, 2021
Tirzepatide
Manufacturer: Eli Lilly
GLP-1, GIP co-agonist
Mounjaro - Brand name for Type 2 Diabetes, weekly injection
FDA Approved May, 2022
Zepbound - Brand name for Weight Loss Application
FDA Approved November, 2023
No pill form (though they are working on it)
If you want more details, I have a quick guide to Semaglutide here and one for Tirzepatide here.
Methodology
This study put the two drugs head to head to see how much weight was lost with each. Half the participants received “the maximum tolerated dose of tirzepatide (10 mg or 15 mg)” and half received “the maximum tolerated dose of semaglutide (1.7 mg or 2.4 mg)” for 72 weeks to see how much weight was lost with each drug. The study was randomized but not blinded, meaning that participants and those conducting the trial knew who was on which drug. Also, there was no placebo group.
Authors
Let’s start, as we always do, with the authors and their extensive financial entanglements with the drug companies. You can see the full disclosures here. The disclosures don’t show the amount of money taken, for that I turn to the OpenPayments database.
Louis J. Aronne, M.D.
Disclosures
Consultant:
Altimune, Amgen, AstraZeneca. Boehringer Ingelheim, Eli Lilly and Company, Jamieson Wellness, Janssen Biotech, Jazz Pharmaceuticals, Novo Nordisk, Pfizer, Senda biosciences, Skye biosciences, Veru
Travel:
Zealand Pharma A/S
Equity Interest, board member:
ERX pharmaceuticals (per their website “ERX developing treatments for ob*sity, leptin sensitizers, novel treatments for ob*sity, ob*sity, metabolic disease, leptin resistance, new ob*sity drugs”
Equity Interest, Board of Directors Member:
Intellihealth (rebranded as FlyteHealth selling “medically supervised weight loss”)
Board of Directors:
Jamieson Wellness (purveyor of weight loss supplements)
Open Payments
Before he switched his focus to diet drugs, Louis published weight loss books. He wrote three books in three decades (1999, 2009, 2017) each claiming to offer the secret to permanent weight loss. I guess not that permanent because now he takes money from the pharmaceutical industry. From 2018 to 2024, he took $254,334.93 in general payments, $4,144.22 in research payments, and $1,232,965.55 in associated research funding, with Novo Nordisk his leading patron for general payments and Eli Lilly leading the way in associated research funding.
Deborah Bade Horn, D.O.
Disclosures
Consultant:
Amgen
Consultant, Advisory Board:
Eli Lilly, Novo Nordisk
OpenPayments
From 2018-2024 she took $705,149.71 in general payments, $47,279.56 in research payments, and $1,027,582.54 in associated research funding. The general payments are almost entirely from Novo Nordisk, the research payments are mostly Novo but also include Lilly, and the associated research funding is entirely Eli Lilly.
Carel W. le Roux, M.D., Ph.D.
Disclosures
Consultant:
AstraZeneca, Boehringer Ingelheim, Currax Pharmaceuticals LLC, Eli Lilly, F. Homann-La Roche AG, Johnson and Johnson, Medtronic, Novo Nordisk
Consultant, Advisory Board:
Arrowhead Pharmaceuticals, Morphic Therapeutic
OpenPayments
He is not from the US and thus isn’t listed in the OpenPayments database.
Wayne Ho, M.D.
From 2018-2024, he took $31,462.41 in general payments, though just a small amount was from Eli Lilly, $20,796.44 in research payments, predominantly from Eli Lilly, and $78,413.73 in associated research funding from Sanofi and Novartis.
Beverly L. Falcon, Ph.D.
Employed by Eli Lilly as a Senior Director - Clinical Research Scientist
Owns stock in Eli Lilly
Elisa Gomez Valderas, M.Sc.
Employed by Eli Lilly as a statistician
Owns stock in Eli Lilly
Sagar Das, M.Sc.
Employed by Eli Lilly as a Biostatistician
Owns stock in Eli Lilly
Clare J. Lee, M.D., M.H.S.
Employed by Eli Lilly as an Executive Vice President
Owns stock in Eli Lilly
Leonard C. Glass, M.D.
Employed by Eli Lilly as a Senior Vice President
Cagri Senyucel, M.D., Ph.D.
Employed by Eli Lilly as Vice President - Global Medical Affairs
Julia P. Dunn, M.D.
Employed by Eli Lilly as Executive Director, Medical
Owns stock in Eli Lilly
In the notes section, the authors write:
“We thank Rhea Lewis, Ph.D., of Eli Lilly for editorial assistance with an earlier version of the manuscript and preparation of the figures, tables, and references before submission of the manuscript; the trial participants and the trial site coordinators and investigators who cared for them; and all the Eli Lilly colleagues who supported the trial, including the trial lead, Rachel Barosh, M.Sc.”
To review, many of the authors took money from the manufacturers of both drugs being studied, but only Eli Lilly supplied statisticians and other authors who are not only employees but also own stock in the company.
With that in mind, in part 2 we’ll take a look at the insights that we can glean from this study.
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More research
The Research Post
More resources
The Resource Post
*Note on language: I use “fat” as a neutral descriptor as used by the fat activist community, I use “ob*se” and “overw*ight” to acknowledge that these are terms that were created to medicalize and pathologize fat bodies, with roots in racism and specifically anti-Blackness. Please read Sabrina Strings’ Fearing the Black Body – the Racial Origins of Fat Phobia and Da’Shaun Harrison’
I love that it took one while article just to talk about how corrupt the authors are for this study 😂
I am looking just at the methodology and author disclosures and WHEWWW talk about a mess.