Tirzepatide has been tested in a randomized withdrawal trial, which is the study design that answers this question directly rather than by inference.
Its result is unambiguous, and it is also not the whole picture. Clinical practice produces a different number, for reasons worth understanding before reading either one as a prediction.
The equivalent evidence for the other GLP-1 drug is in what happens when you stop taking semaglutide.
The withdrawal trial
SURMOUNT-4 enrolled 783 adults with obesity or overweight and gave all of them open-label tirzepatide for 36 weeks, at the maximum tolerated dose of 10 or 15 mg [1]. Mean weight fell 20.9% during that period.
At week 36, the 670 participants who completed the lead-in were randomly assigned, half continuing tirzepatide and half switching to placebo for another 52 weeks.
| Outcome | Continued tirzepatide (n=335) | Switched to placebo (n=335) |
|---|---|---|
| Weight change, week 36 to 88 | −5.5% | +14.0% |
| Kept at least 80% of the lead-in loss | 89.5% | 16.6% |
| Overall change, week 0 to 88 | −25.3% | −9.9% |
| Discontinued study drug after randomization | 10.4% | 17.9% |
The difference between the two arms over those 52 weeks was −19.4% (95% CI −21.2 to −17.7, P < .001). Regain on placebo was not partial; the group gave back most of what it had lost.
One number in that table is easy to miss. The placebo group still finished 9.9% below where it started, after a year of regaining, so 88 weeks of treatment and withdrawal did not return people to baseline.
The label records the same trial and adds the dropout figures [3]. It also notes that 93% of randomized participants were on 15 mg at the end of the lead-in, which is the top of the ladder described in tirzepatide dosage.
What survived a gap in a longer trial
SURMOUNT-1 followed 1,032 participants who had both obesity and prediabetes for 176 weeks on treatment, then took them off it for 17 weeks [2].
At 176 weeks the mean weight change was −12.3% on 5 mg, −18.7% on 10 mg and −19.7% on 15 mg, against −1.3% on placebo.
Type 2 diabetes had been diagnosed in 1.3% of the tirzepatide groups against 13.3% on placebo (HR 0.07, 95% CI 0.0 to 0.1). After the 17-week off-treatment period those figures were 2.4% and 13.7% (HR 0.12, 95% CI 0.1 to 0.2).
So the diabetes gap narrowed after stopping and did not close. Seventeen weeks is a short window, and the trial was not designed to follow that gap further.
What happens outside a trial
A retrospective cohort at a large health system tracked 7,938 adults who started injectable semaglutide or tirzepatide and stopped within three to 12 months [4].
Mean weight change from starting to stopping was −8.4% (95% CI −8.7 to −8.1) among those treated for obesity. In the year after stopping, mean weight change was +0.5% (95% CI 0.0 to 1.0).
That is far less regain than the trial. The authors are explicit that individual-level variability was considerable, so the average conceals people who regained a great deal and people who kept losing.
Two things explain most of the gap. Trial participants reached a much larger loss before stopping, and people in practice do not simply stop and do nothing.
In that cohort, 19.6% restarted the same medication within a year and 35.2% received some other obesity treatment, including 27.4% who started a different medication [4].
Why the weight comes back
A 2026 review of discontinuation describes the pattern as a biological response rather than a failure of resolve [6]. Appetite signaling returns to its pre-treatment state, and the cardiometabolic gains recede alongside the weight.
That pattern is visible in the trial data. Weight, blood pressure and lipid measures moved together in both directions in SURMOUNT-4 [1].
What the lost weight was made of also matters, since some of it is lean mass and regained weight is not necessarily the same tissue. That is covered in GLP-1 muscle loss.
Putting it together
The randomized answer is that stopping tirzepatide after a large loss leads to substantial regain, and that continuing leads to further loss. The real-world answer is that average regain is small and the spread around it is wide.
Both are true, and they describe different populations: one that stopped at 20.9% down by protocol, and one that stopped for cost, side effects or supply after a smaller loss.
For what the loss looks like while treatment continues, see how much weight you can lose on tirzepatide. To compare prescribers by monthly cost, see the compounded tirzepatide rankings, and for the rest of this goal, the weight hub.