Peer-reviewed withdrawal studies consistently show substantial regain when weight-loss treatment stops without a plan: roughly two-thirds of lost weight returns within a year in the STEP-1 extension data, and SURMOUNT-4 found a mean 14% regain in the year after switching to placebo. Every statistic on this page is from a peer-reviewed journal or the NHS, with the citation alongside.
This page exists to be cited. Each number below links to its primary source, and the page is reviewed and dated. If you are a journalist, researcher or clinician, you are welcome to quote it with attribution.
One year after stopping a weekly GLP-1 weight-loss injection (and ending lifestyle support), participants in the STEP-1 extension had regained around two-thirds of their lost weight — and cardiometabolic improvements (blood pressure, lipids, HbA1c) largely reverted toward baseline.
In SURMOUNT-4, adults lost a mean 20.9% of body weight in a 36-week lead-in. Those then switched to placebo regained a mean 14% over the following 52 weeks; those who continued treatment lost a further 5.5%.
In STEP-4, after a 20-week run-in (mean 10.6% weight loss), participants switched to placebo regained 6.9% over 48 weeks while those continuing weekly treatment lost a further 7.9% — a statistically significant difference.
The NHS estimates around 1 in every 4 UK adults is living with obesity — the population for whom the question of what happens after treatment is most consequential.
The NHS notes that losing as little as 3% of original body weight — and maintaining it for life — can significantly reduce the risk of obesity-related complications such as type 2 diabetes and heart disease. Maintenance, not the maximum number on the scale, is the clinically meaningful outcome.
Three things are worth holding together. First, these are averages from trials in which treatment stopped without a structured transition — they describe what happens by default, not what must happen. Second, regain is mechanistic, not moral: appetite-regulating treatment ends, appetite returns, and whatever habits exist at that moment take over. Third, the modifiable variable is what is in place when treatment ends — nutrition, muscle, monitoring and routine. That is the case for treating the finish as a planned phase: a weight-loss off-ramp.
Aion Society, “Weight regain after stopping treatment: the key statistics”, aionsociety.co.uk/off-ramp-statistics.html, updated 10 June 2026. Please retain the primary-source citations when quoting individual figures.
Primary sources: doi:10.1111/dom.14725 · doi:10.1001/jama.2023.24945 · doi:10.1001/jama.2021.3224 · NHS — Obesity
Related reading: What is a weight-loss off-ramp? · Weight regain: why it happens · Coming off (full guide) · The science
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