Zepbound produced 20.9% mean weight loss against Foundayo's 11.1%, and caused nausea in 28% of patients against Foundayo's 35%. It is the stronger drug and the better tolerated one at the same time. There is no trade to explain here, which makes this the most straightforward comparison in the category and the least comfortable one for the tablet.
Side by side
| Foundayo | Zepbound | |
|---|---|---|
| Molecule | Orforglipron | Tirzepatide |
| Targets | GLP-1 | GLP-1 and GIP |
| Form | Daily tablet | Weekly injection |
| Mean weight loss | 11.1% at 72 weeks | 20.9% at 72 weeks |
| Nausea | 35% | 28% |
| Vomiting | 24% | 13% |
| Stopped for side effects | 8% | ~10% (with lifestyle lead-in) |
| Self-pay from | $149 | $349–$499 |
| Also approved for | — | Obstructive sleep apnoea |
| Maker | Eli Lilly — both | |
Both are Eli Lilly products, which is worth noting: the company sells the weaker tablet and the stronger injection, and prices them accordingly.
The efficacy gap is the largest in the approved class
Nine and a half percentage points separate these two. On a 100 kg starting weight that is roughly ten kilograms — not a refinement, a different outcome.
| Proportion who lost | Foundayo 17.2 mg | Tirzepatide 15 mg |
|---|---|---|
| At least 5% | 71.5% | ~91% |
| At least 10% | 54.5% | ~84% |
| At least 15% | 35.9% | ~71% |
| At least 20% | 18.4% | ~57% |
The responder rows widen the gap rather than closing it. Roughly one in five Foundayo patients reached 20% weight loss; on tirzepatide it was more than half.
These are separate trials — Foundayo's phase 3 programme and SURMOUNT-1 — so the exact numbers are not a head-to-head. Nothing about a fairer comparison would close a nine-point gap.
And it is easier to take
The usual expectation is that the more powerful drug is the harsher one. Here it is the opposite.
| Adverse reaction | Foundayo 17.2 mg | Zepbound 15 mg |
|---|---|---|
| Nausea | 35% | 28% |
| Vomiting | 24% | 13% |
| Constipation | 24% | 11% |
| Diarrhoea | 25% | 23% |
| Hair loss | 5% | 5% |
Zepbound is lower on four of five rows and level on the fifth, with vomiting and constipation roughly half. The same pattern appeared in the head-to-head between tirzepatide and semaglutide, where the stronger molecule was also the better tolerated one. Tirzepatide is simply an unusually favourable drug on this axis.
One number does run the other way: about 10% of Zepbound patients discontinued for adverse reactions in the trial with a lifestyle lead-in, against 8% on Foundayo. Discontinuation and incidence measure different things, and on incidence Zepbound wins clearly.
So what is Foundayo for
Two things, and they are real.
It is a tablet with no rules. Once daily, with or without food, no water limit, no waiting. For someone who will not inject — and that is a large group, not a marginal one — the comparison above is between a drug they will take and a drug they will not. An 11.1% result you actually achieve beats a 20.9% result you decline.
It is much cheaper. $149 a month at the starting dose against $349 to $499 for Zepbound vials, and $299 at the top dose with the savings card. Over a year at maintenance that is a difference of hundreds to low thousands of dollars, and it is the difference between affordable and not for plenty of people.
What Foundayo is not is a stealth equal. Anyone choosing it should know they are choosing roughly half the weight loss, and choosing it for the form or the price rather than in spite of them.
Two things only Zepbound has
An approval for obstructive sleep apnoea. Zepbound is indicated for moderate-to-severe OSA in adults with obesity, which matters both clinically and for insurance: a second diagnosis is a second route to coverage.
A second receptor. Tirzepatide activates GIP as well as GLP-1, and the leading explanation for the efficacy gap is that second target. Foundayo is a single-receptor drug in a market moving toward dual and triple agonists — how that field is developing is in the GLP-1 pipeline tracker, and the dual mechanism itself in how tirzepatide works.
Which one
- Most weight lost: Zepbound, by nine and a half percentage points. Not close.
- Best tolerated: Zepbound, on four of five reactions.
- Will not inject: Foundayo, and this is the reason that decides it for most people who choose it.
- Cost: Foundayo, from $149 against $349–$499.
- Sleep apnoea: Zepbound, the only one approved for it.
- Complicated medication list: Zepbound. Foundayo interacts through CYP3A4 in ways a peptide does not — see Foundayo dosage.
The honest summary is that Zepbound wins the drug comparison and Foundayo wins the delivery comparison. Which of those you are actually choosing between is the question, and it is one for a clinician who knows the rest of your history. The wider ranking is in the best GLP-1 for weight loss.
The other comparisons
Against semaglutide the picture is less one-sided: Foundayo vs Wegovy is a genuine trade, with the tablet weaker on weight and gentler on nausea. And Foundayo vs Ozempic compares a weight-approved drug with one that is not approved for weight at all.
Scientific References
3 sources- 1
Eli Lilly and Company
FOUNDAYO (orforglipron) tablets — Prescribing Information, §6.1 Table 1, §14 Table 6
DailyMed, U.S. National Library of Medicine · 2026
NIH - 2
Eli Lilly and Company
ZEPBOUND (tirzepatide) injection — Prescribing Information, §1, §6.1
DailyMed, U.S. National Library of Medicine · 2026
NIH - 3
Jastreboff AM, Aronne LJ, Ahmad NN, et al.
Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1)
New England Journal of Medicine · 387(3) · 2022PMID: 35658024
NEJM
References open in a new tab. Content is reviewed against peer-reviewed literature as part of our editorial policy.
About the author
Editor, Modern Weight Science
Claudiu Gheorghe is the editor of Modern Weight Science. He is not a physician. His role is to synthesize peer-reviewed studies, clinical-trial data, and FDA prescribing information into clear, plain-language explanations, and to make sure every factual claim on the site traces back to a cited source. Any decision about starting, changing, or stopping a medication belongs with a licensed clinician who knows your history.
Every claim is checked against peer-reviewed research through our review process and fact-checking policy.
Frequently Asked Questions
Is Foundayo as effective as Zepbound?
No, and the gap is the largest between any two approved weight-loss drugs: 11.1% mean weight loss against 20.9%, roughly ten kilograms on a 100 kg starting weight. The responder figures widen it further — 18.4% of Foundayo patients lost at least 20% of body weight against more than half on tirzepatide.
Which has worse side effects, Foundayo or Zepbound?
Foundayo, which is the opposite of what most people expect from the weaker drug. Nausea 35% against 28%, vomiting 24% against 13%, constipation 24% against 11%. Zepbound is lower on four of five common reactions and level on hair loss. The same pattern appeared when tirzepatide was compared head-to-head with semaglutide: the stronger molecule was also the better tolerated one.
Why would anyone choose Foundayo over Zepbound?
Two reasons, both real. It is a tablet with no food or water rules, which matters for the large group of people who will not use an injection — an 11.1% result you take beats a 20.9% result you decline. And it is much cheaper: from $149 a month against $349 to $499 for Zepbound vials. What Foundayo is not is a quiet equal; anyone choosing it should know they are choosing roughly half the weight loss.
Are Foundayo and Zepbound made by the same company?
Yes, both are Eli Lilly products. Foundayo is orforglipron, an oral small molecule acting on the GLP-1 receptor; Zepbound is tirzepatide, an injected peptide acting on GLP-1 and GIP. The second receptor is the leading explanation for the efficacy gap.
Is Zepbound approved for anything Foundayo is not?
Yes — moderate-to-severe obstructive sleep apnoea in adults with obesity. That matters clinically and practically, since a second diagnosis can open a second route to insurance coverage. Foundayo is approved for weight reduction only.
Continue learning
Where to read next
Not medical advice. This guide is for general education only. GLP-1 medications, dosing, and treatment suitability are decisions for you and a licensed clinician who knows your full medical history.