EP 152:28

What happens when you stop a GLP-1

Name: What happens when you stop a GLP-1
Uploaded: 2026-09-28
Duration: 2 min 28 s
Description: The drug leaves within weeks and much of the weight returns, though on average not all of it. The trials where people switched to placebo, why the body defends against weight loss, and what helped in studies.

The drug leaves within weeks and much of the weight returns, though on average not all of it. The trials where people switched to placebo, why the body defends against weight loss, and what helped in studies.

Transcript and sources

One year after stopping, two thirds of the weight came back. And yet, people were still lighter than when they started. Here's what actually happens when you stop a GLP-1.
First, the drug leaves. Semaglutide's half-life is about a week, and the label says it stays in the blood for about five to seven weeks after the last dose. Tirzepatide's half-life is about five days.
The clearest test is a fork. In SURMOUNT-4, everyone took tirzepatide first, then half were switched to placebo. They regained fourteen percent of their body weight over a year, while those who stayed on lost another five point five.
Semaglutide's version, STEP 4, showed the same pattern. Switched to placebo, people regained six point nine percent; those who continued lost another seven point nine.
And it isn't just weight. After stopping, blood pressure and other heart and metabolic markers drifted back toward where they started.
A 2026 review in the BMJ pooled thirty-seven studies. Weight came back faster after stopping weight-loss medicines than after diet-and-exercise programmes, even allowing for how much was lost.
Why? The body defends against weight loss. In one diet study, a year later, hunger hormones like ghrelin and leptin still hadn't returned to their old levels, and people felt hungrier.
After weight loss, the body also burns less energy than its new size alone would predict.
But regain isn't total. Another 2026 review found about sixty percent of lost weight returned in the first year, and the curve was slowing.
Some things helped in studies. In a tirzepatide trial, people who stepped down to a lower dose kept more weight off than those switched to placebo. And in a liraglutide study, people who'd exercised alongside the drug regained less after everything stopped.
Stopping is common. In a large US health-records study, about sixty-five percent of people without diabetes stopped their GLP-1 within a year, and in one poll, cost and side effects were the top reasons.
The drug leaves in weeks, but the body remembers. Every study is at peplexicon.com.

Sources