This paper publishes two percentages. They are not two versions of one answer. They measure different things, and only one of them answers what a buyer wants to know.
The number most people will quote
Six studies were pooled. In them, 5,553 adults stopped their GLP-1 and 3,440 stayed on it. [1] The difference in weight between those two groups came to 17.90%, with an interval of 14.11 to 21.69.
Read it carefully. It is a gap, and a gap has two sides. The people still taking the drug were still losing. The people who stopped were gaining. The 17.90% is both of those added together, so it describes a distance between two futures rather than a weight anybody put back on.
What that means for a year of paying
Most of the loss is rented, not bought. That is the honest summary.
It also lands on an audience that mostly does not last a year. Retention data shows most people stopping inside six months, which means the regain figure applies to the majority rather than to an unlucky few.
The pace matters too, and this paper does not give one. For that you need the studies that tracked the curve month by month.
The six studies disagree
Heterogeneity tested at P = 0.0082. In plain terms, the six results are further apart than chance explains.
A pooled average across disagreeing studies is still useful. It is just less precise than the interval printed beside it suggests, and the interval is already fairly wide.
The authors also report larger rebound after tirzepatide than after semaglutide. No trial compared the two withdrawals head to head. That is a comparison assembled across separate studies, which is the weakest shape a drug comparison comes in.
What gets better when you stop
Side effects. Overall adverse reactions fell after withdrawal, and gastrointestinal ones fell specifically.
Cardiovascular event rates did not change either way. So stopping is not only a loss column, and anyone selling a long prepay should not be allowed to imply otherwise — the same arithmetic that decides whether a year of this is worth its price has to carry the regain on one side and the side effects on the other.
How to use it
Budget for the drug as an ongoing cost, not a course. Expect roughly 9% of your body weight back if you stop, on this evidence.
And if the plan is to stop at a target, plan the stop itself. Dose matters to whether people stay at all, which is its own decision — the dose people actually stay on is rarely the one on the label.