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Zepbound for Weight Loss: The 20.9% Is a Group Average

Find Peptide Clinics Editorial Desk

Zepbound for weight loss produces a mean 20.9% reduction. That figure comes from a trial that excluded people with type 2 diabetes, and about one in ten patients on the top dose had no weight recorded at week 72 at all.

The flat answer first. In SURMOUNT-1, adults without diabetes on the 15 mg dose lost a mean 20.9% of body weight by week 72 against 3.1% on placebo. In a separate withdrawal trial, patients who stopped regained a mean 14.0% within a year while those who continued lost another 5.5% (NEJM, June 4, 2022; JAMA, December 11, 2023). That sentence is a group statistic.

Zepbound for Weight Loss – What the FDA Approved and When

The FDA approved Zepbound (tirzepatide) for chronic weight management on November 8, 2023. The labeled population: adults with a BMI of 30 or higher, or 27 or higher with at least one weight-related condition, alongside a reduced-calorie diet and more physical activity (FDA release, November 8, 2023).

John Sharretts, who directs the FDA division covering obesity drugs, framed the approval around unmet need. The agency’s release put the size of that need at roughly 70% of American adults living with obesity or overweight.

The label on file now, revised August 2026, carries a second indication: moderate to severe obstructive sleep apnea in adults with obesity. It also carries a Limitations of Use line worth reading twice. Zepbound does not combine with another tirzepatide product or with any GLP-1 receptor agonist (DailyMed, Zepbound prescribing information).

The boxed warning at the top of that label is the first thing to read. Tirzepatide caused thyroid C-cell tumors in rats at clinically relevant exposures. The label states that human relevance has not been determined, and it contraindicates Zepbound for anyone with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2.

The Trial Table – 20.9% Is a Mean, and Means Have Edges

SURMOUNT-1 enrolled 2,539 adults with a BMI of 30 or higher, or 27 or higher plus a weight-related condition, and excluded type 2 diabetes. Patients received placebo or 5, 10 or 15 mg across 72 weeks, including a 20-week dose-escalation period (NCT04184622).

Mean starting weight was 104.8 kg, about 231 pounds. At week 72 the label’s table reads: 3.1% lost on placebo, 15.0% on 5 mg, 19.5% on 10 mg, 20.9% on 15 mg. The share losing at least 5% of body weight ran 34.5% on placebo, then 85.1%, 88.9% and 90.9%. The share losing 20% or more: 50% on 10 mg and 57% on 15 mg, against 3% on placebo (DailyMed, Table 2).

Then the column that does not make the advertising. Body weight at week 72 was missing for 21.6% of the placebo arm and 9.4% of the 15 mg arm. A mean built from the patients who stayed describes the patients who stay.

Read that missing-data line before the headline. At week 72, body weight was not recorded for 21.6% of the placebo arm and 9.4% of the 15 mg arm. The label gives no reason for the gap, so neither figure measures who quit; they measure who has no week-72 weight on file.

SURMOUNT-4 – The Year After You Stop

This is the trial that answers the question people type at month three. Seven hundred eighty-three adults went through a 36-week open-label lead-in on the maximum tolerated dose of 10 or 15 mg. They lost a mean 20.9%, matching the headline number. Six hundred seventy of them then randomized to keep the drug or switch to placebo for 52 more weeks (NCT04660643).

The continuing group lost another 5.5%. The withdrawing group gained 14.0%. The gap between the arms was 19.4 percentage points, and 89.5% of continuing patients held on to at least 80% of their earlier loss against 16.6% of the placebo arm. Weight change from week 0 to week 88 came to 25.3% lost with continued treatment versus 9.9% for the group that stopped (JAMA, December 11, 2023).

Follow one representative body through that arithmetic. A patient starting at 104.8 kg sits near 82.9 kg after the lead-in, and the withdrawal path adds 14.0% back: roughly 94.5 kg, or about 208 pounds from a 231-pound start. Honest caveat, stated plainly: this was a randomized withdrawal design among people who had already tolerated the drug for 36 weeks. It measures what stopping costs that population. It does not forecast any single person’s year, and it is not a reason to stay on a drug that made you sick.

The Label’s Dose Grid – 2.5 mg Is a Starting Dose and Nothing More

The label opens at 2.5 mg once weekly for four weeks and states that 2.5 mg is for treatment initiation, not for maintenance. Steps go up by 2.5 mg no sooner than four weeks apart. Maintenance for weight reduction runs 5, 10 or 15 mg once weekly, with 15 mg as the labeled maximum (DailyMed, sections 2.1 and 2.2). The label sets a schedule. A prescriber sets a person’s dose, and that is the only place a dose should come from.

The tolerance numbers explain why the schedule exists. In the pooled weight-management trials, severe gastrointestinal reactions were reported in 1.7% of patients on 5 mg, 2.5% on 10 mg and 3.1% on 15 mg, against 1% on placebo. Permanent discontinuation for adverse reactions: 4.8%, 6.3% and 6.7%, against 3.4% on placebo. Nausea ran 25%, 29% and 28% against 8%. Diarrhea 19%, 21% and 23% against 8%. Vomiting 8%, 11% and 13% against 2% (DailyMed, section 6.1). For a fuller breakdown of which reactions cluster where, our label numbers piece on tirzepatide walks the same tables dose by dose.

Type 2 Diabetes – The Group Study 1 Left Out

If you have type 2 diabetes, the 20.9% headline was not measured on you. Study 2 ran the same 72-week design in 938 adults with a BMI of 27 or higher and type 2 diabetes. Mean weight change came to 12.8% on 10 mg and 14.7% on 15 mg, against 3.2% on placebo (DailyMed, section 14.1). Same molecule, different trial population, a visibly smaller number.

That distinction also runs through the brand names. Tirzepatide sold as Mounjaro carries the type 2 diabetes indication; sold as Zepbound it carries weight management and sleep apnea. The molecule did not change between the labels. The studied group did. Our step-by-step reading of the Mounjaro schedule covers the diabetes side of the same drug.

Compounded Tirzepatide – The Shortage Ended and the Copies Did Not

For two years, the legal footing under compounded tirzepatide was a national shortage. That footing is gone. The FDA determined the tirzepatide injection shortage resolved on December 19, 2024, and its enforcement discretion for state-licensed pharmacies ended February 18, 2025 (March 19, 2025 for outsourcing facilities) after a district court denied the related injunction motion on March 5, 2025 (FDA, compounding policy updates).

The agency’s page, updated April 1, 2026, states the position in plain language: “Tirzepatide and semaglutide do not currently appear on the 503B bulks list or on FDA’s drug shortage list.” It also spells out the essentially-a-copy restriction and says the agency does not intend to act against a compounder filling four or fewer prescriptions of that compounded product in a calendar month.

On April 30, 2026 the FDA proposed excluding semaglutide, tirzepatide and liraglutide from the 503B bulks list, with comments open through July 30, 2026 (FDA release, April 30, 2026). As of October 22, 2026, no published final determination exists, so the proposal remains a proposal, and how it lands is not knowable yet. The line the FDA has drawn without ambiguity: a compounded drug is not an FDA-approved drug, and a compounded copy of tirzepatide is not Zepbound.

Frequently asked questions – Zepbound for Weight Loss

How much weight do people lose on Zepbound?

The labeled trial mean at 15 mg ran 20.9% of body weight at 72 weeks in adults without diabetes, with 57% of that arm losing 20% or more. Half of the 10 mg arm reached 20%. A third of the placebo arm lost at least 5%.

Is Zepbound FDA-approved for weight loss?

Yes. The FDA approved it on November 8, 2023 for chronic weight management in adults with a BMI of 30 or higher, or 27 or higher with at least one weight-related condition. The current label adds moderate to severe obstructive sleep apnea in adults with obesity.

Do you gain the weight back after stopping Zepbound?

In SURMOUNT-4, the group that stopped regained a mean 14.0% over 52 weeks while the group that continued lost another 5.5%. That was a randomized withdrawal among people who had already tolerated 36 weeks of treatment, so it describes a population, and it is the best-controlled evidence available on the question.

Is Zepbound the same as Mounjaro?

Same active ingredient, tirzepatide. Different approved uses: Mounjaro for type 2 diabetes, Zepbound for weight management and sleep apnea. The weight-loss percentages also differ by studied group, with 12.8% and 14.7% at 10 mg and 15 mg in the diabetes trial against 19.5% and 20.9% in the trial that excluded diabetes.

Can I still get compounded tirzepatide?

The shortage that permitted large-scale compounding resolved in December 2024, and FDA’s stated position is that tirzepatide appears on neither the 503B bulks list nor the shortage list. A compounded product is not FDA-approved, it is not the drug in these trials, and the regulatory picture is still moving. Ask a licensed pharmacy and a prescriber what they can lawfully dispense, and treat any seller promising guaranteed supply as a warning sign.

How long does Zepbound take to work?

The labeled efficacy endpoint sits at 72 weeks, and dose escalation alone runs 20 weeks. The label publishes no week-4 or week-8 weight-change figure, so no honest early number exists to quote from it. The earliest large mean available is the 36-week lead-in of SURMOUNT-4, where patients on the maximum tolerated dose reached a mean 20.9% reduction.

Sources

This article is reporting on published labels and trial results for a directory of clinics and patients. It is not medical advice, and it does not tell anyone what to take.