Most adults who stayed on tirzepatide for three years in the SURMOUNT-1 trial put back only a small part of what they had lost after reaching their lowest weight, according to a post hoc analysis published in Obesity Pillars. Of 690 participants with prediabetes who took at least three-quarters of their doses and lost at least 5% of their body weight, 70% regained less than 5% of their starting weight between their low point and week 176. For people watching the scale creep up after a plateau, it puts a number on what is typical.
What the analysis found
SURMOUNT-1 randomised adults with obesity, or overweight with at least one weight-related condition, to weekly tirzepatide at 5 mg, 10 mg or 15 mg, or to placebo. Those who had prediabetes at enrolment — 1,032 people, 762 of them on tirzepatide — were followed for 176 weeks. This analysis kept the 690 tirzepatide participants, 90.6% of that group, who were adherent and had lost at least 5% at their lowest point. Placebo participants were not part of it.
Average loss at the low point was 19.0%, 24.3% and 26.0% across the three doses. By week 176 it was 15.5%, 20.1% and 22.5%. The gap is the regain: on average 3.8 kg, 4.4 kg and 3.7 kg, or 3.5% to 4.1% of starting weight. The low point came late, a mean of 21 to 23 months in, and more than half of participants reached it after week 72.
Pooled across doses, 484 people (70%) regained under 5% of their starting weight, 149 (22%) regained 5% to under 10%, and 57 (8%) regained 10% or more. The median share of the peak loss still held at week 176 was 94.8%, 69.9% and 44.3% in those three groups. Waist-to-height ratio moved the same way: the share whose risk category worsened between the low point and week 176 was 6.4%, 24.3% and 36.8%. Blood sugar held up better. At week 176, 96.1%, 92.6% and 91.2% of the three groups had normal glucose.
This site has covered what happens when people stop these drugs, where pooled trial data show weight returning at roughly a kilogram a month. This analysis asks a different question: whether weight drifts back while treatment continues. Its answer, for this selected group, is that some drift is the norm and large rebounds are uncommon. Even the highest-regain group on the 15 mg dose was still about 10% below its starting weight at week 176.
The authors describe 92% of participants as having a stable weight journey. That figure adds the under-5% and the 5%-to-under-10% groups together, so it counts as stable someone who put back nine points of starting weight; the 149 people in that middle group kept a median of 70% of their peak loss. The underlying split, 70, 22 and 8, is the more useful number. For the wider evidence on the drug, including the rest of the SURMOUNT programme, see our tirzepatide research page.
What this does not show
This is a post hoc analysis, planned after the trial, and it was funded by Eli Lilly, which makes tirzepatide; five of its eight authors are Lilly employees. It includes only people who took at least 75% of their doses and lost at least 5%, so it says nothing about people who stopped, missed doses or responded less. Everyone had prediabetes; people with type 2 diabetes were excluded. Missing week-176 weights were filled with the last value recorded, which can understate regain if people left while gaining. Blood pressure, lipids and glucose were measured only at baseline, week 72 and week 176, and most participants reached their low point after week 72, so the links between regain and those markers are loose. There is no placebo comparison, and the group results are descriptive, with no confidence intervals for the comparisons between them.
Sources: Aronne LJ, Vincent RP, Klein KR, et al. Evaluation of clinical relevance of weight nadirs and weight regain during 3 years of treatment with tirzepatide in participants with obesity or overweight and prediabetes. Obesity Pillars, volume 20, article 100333, published online 18 September 2026 (open-access full text). Trial registration NCT04184622.
