The short answer
Slowing weight loss was common among selected trial participants who responded to tirzepatide. The study's definition of a plateau did not mean absolutely no change on the scale.
How was a plateau defined?
Researchers counted a plateau when weight changed by less than 5% across a 12-week interval and every later 12-week interval. They dated it from the beginning of that first interval.
Weeks; plateau does not mean zero weight change
Original visual based on the study.
| Group or measure | Result |
|---|---|
| Overweight | 24.3 weeks |
| Class I obesity | 26.0 weeks |
| Class II or III obesity | 36.1 weeks |
Who was included?
This secondary analysis included 1,438 participants from SURMOUNT-1 and 259 from SURMOUNT-4 who adhered to tirzepatide and achieved at least 5% weight loss by the trial endpoint.
What did researchers find?
In SURMOUNT-1, the median time to plateau was:
Overweight: 24.3 weeks.
Class I obesity: 26.0 weeks.
Class II or III obesity: 36.1 weeks.
These describe baseline BMI groups, not a personal timetable.
The useful takeaway
A slower pace can occur after a substantial response. This exploratory analysis cannot tell someone when to change treatment. Its selected population, small subgroups and visit-based definition limit how broadly the timing applies.
Sources
Horn and colleagues, Clinical Obesity, 2025. Funded by Eli Lilly.