Is there a published regain percentage for retatrutide?

No. The phase 2 obesity trial measured body weight only through week 48 of treatment, and the phase 3 TRIUMPH-1 results released in May 2026 report on-treatment weight through week 80 and week 104. Any specific retatrutide regain figure circulating online is borrowed from another drug or invented.

When will we know what happens after stopping retatrutide?

TRIUMPH-6 is the randomized withdrawal study. It gives everyone retatrutide for 80 weeks, then randomizes people for 36 weeks to continue, escalate, or switch to placebo. Its primary completion date is April 2028.

Does regain go all the way back to the starting weight?

In the pooled GLP-1 analysis it did not. Regain plateaued at about 75 percent of the weight lost, leaving people below their pretreatment weight. Individual results vary widely, and that model was built on six randomized trials of other drugs.

Can diet and exercise hold the weight off after stopping?

The withdrawal trials all continued lifestyle support after the drug stopped, and regain still happened. Lifestyle measures matter and may slow regain, but the published evidence does not show them fully replacing the medication effect.

Does stopping reverse the health improvements too?

In the STEP 1 extension, cardiometabolic measures improved during treatment and then drifted back toward baseline in the year after withdrawal. The weight and the metabolic benefits moved together. No equivalent data exists for retatrutide.

Do You Regain Weight After Stopping Retatrutide?

The short answer: No completed retatrutide trial has published body weight data from an off-treatment period, so the honest answer is that nobody has measured it yet. The phase 2 obesity trial dosed people for 48 weeks and stopped measuring weight there. Evidence from semaglutide and tirzepatide, which act on some of the same receptors, shows most people regain a large share of the lost weight within a year of stopping. A phase 3 retatrutide withdrawal study is running now, with results due in 2028.

Has any retatrutide trial measured weight after people stopped?

Not in any published result. The phase 2 obesity trial randomized 338 adults to retatrutide or placebo for 48 weeks. The ClinicalTrials.gov record lists every body weight outcome at week 24 and week 48 only. At week 48 the mean weight reduction was 24.2 percent on the 12 mg dose and 2.1 percent on placebo.

The same record shows adverse events collected "Baseline Through End of Safety Follow-up (Up to 52 Weeks)". That is roughly four weeks after the last dose, and it covers safety, not body weight. So the trial that produced the headline weight loss numbers never reported what happened to weight off the drug. If you see a regain percentage for retatrutide quoted online, ask where it came from. For what the on-treatment numbers actually say, see how much weight people lose on retatrutide.

Retatrutide is also still investigational. Eli Lilly states it is legally available only to people in its clinical trials.

What is the TRIUMPH program testing about stopping?

One phase 3 study is built around this exact question. TRIUMPH-6 is a randomized withdrawal design. Every participant takes retatrutide for an 80 week lead-in. Then they are randomized for 36 weeks to stay on the same dose, move to a higher dose, or switch to placebo. The planned enrollment is 643 people and the primary endpoint is percent change in body weight at week 116.

TRIUMPH-6 started in March 2025 and its primary completion date is April 2028. No results are posted. Note the design detail: switching to blinded placebo inside a trial is not identical to stopping in ordinary life, but it is the closest controlled test available.

The main obesity trial, TRIUMPH-1, enrolled 2,335 participants and ran 80 weeks of treatment. Lilly reported on 21 May 2026 a mean reduction of 28.3 percent on 12 mg at week 80, against 2.2 percent on placebo. That release contains no off-treatment weight data either. The doses tested are covered in our guide to retatrutide trial doses.

What happened when people stopped semaglutide or tirzepatide?

This is the best available proxy, and the pattern is consistent across three trials.

STEP 1 extension. 1,961 adults took semaglutide 2.4 mg or placebo for 68 weeks, then everyone stopped and was followed for a further year. Semaglutide users had lost 17.3 percent of body weight at week 68. They regained 11.6 percentage points, leaving them 5.6 percent below baseline at week 120. That is two thirds of the loss returned. Blood pressure, lipids and other cardiometabolic measures drifted back toward baseline as well.
STEP 4. A 68 week withdrawal study. After a 20 week run-in that produced 10.6 percent weight loss, people who continued semaglutide lost a further 7.9 percent from week 20 to week 68. People switched to placebo gained 6.9 percent over the same window.
SURMOUNT-4. A 36 week open-label tirzepatide lead-in produced 20.9 percent mean weight reduction. From week 36 to week 88, people who stayed on tirzepatide lost another 5.5 percent. People switched to placebo gained 14.0 percent.

Our sibling site covers the semaglutide side of this in more depth in its piece on weight regain after Ozempic.

How fast does the weight come back?

A 2026 systematic review and nonlinear meta-regression in eClinicalMedicine pooled data on stopping GLP-1 receptor agonists. It screened 48 studies, and six randomized trials with 3,236 participants fed the model.

The findings were specific. One year after stopping, 60 percent of the weight lost on treatment had come back. Regain then decelerated and plateaued at 75.3 percent of the weight lost (95 percent CI 68.9 to 81.6). The modeled half-life of regain was 23.0 weeks.

Two things follow. Regain is fast at first and slows down. It also tends to stop short of the original starting weight, so a quarter of the loss held in the pooled model. That is a real but much smaller result than the on-treatment number.

Why does the body push the weight back on?

Several mechanisms stack up, and each one is documented separately.

Appetite returns. In a controlled study, semaglutide cut ad libitum daily energy intake by 24 percent and reduced hunger and food cravings. Those effects depend on the drug being present.
Gastric emptying speeds up again. Semaglutide delayed first-hour gastric emptying in people with obesity. Remove the drug and meals empty at the usual rate, so the early fullness signal fades.
Hormonal adaptation outlasts the weight loss. One year after diet-induced weight loss, ghrelin, leptin and subjective hunger had not returned to pre-loss levels. The body keeps signaling for more food.
Energy expenditure stays lower. Six years after large weight loss, resting metabolic rate in one cohort was 704 kcal/day below baseline, with metabolic adaptation of 499 kcal/day beyond what body size predicted.

One caution. None of this was measured with retatrutide. Retatrutide adds a glucagon receptor component that semaglutide and tirzepatide do not have, so the off-treatment pattern may not match them exactly. Until TRIUMPH-6 reports, that is an open question rather than a known difference.

What does stopping and restarting do to muscle?

A body composition substudy of the phase 2 retatrutide trial in type 2 diabetes used DXA scans at week 36. Total fat mass fell 26.1 percent on 8 mg, 23.2 percent on 12 mg and 15.2 percent on 4 mg, against 4.5 percent on placebo. The authors reported that the proportion of lean mass loss to total weight loss was similar to other obesity treatments.

What that lean mass does after the drug stops has not been measured for retatrutide. Any claim that regained weight returns purely as fat is not established for this medicine. Resistance training and adequate protein are standard advice during weight loss for lean mass protection, and that advice does not change off treatment. We cover the on-treatment picture in does retatrutide cause muscle loss.

The bottom line

There is no retatrutide-specific answer yet, and anyone quoting one is extrapolating. The trial designed to answer it, TRIUMPH-6, reports in 2028. Every comparable drug studied so far shows substantial regain after stopping, with roughly 60 percent of the loss back at one year and a plateau near 75 percent.

That is why the 2025 American Association of Clinical Endocrinology consensus statement describes adiposity-based chronic disease as a complex, chronic disease that necessitates long-term treatment and care. If and when retatrutide reaches the market, the sensible planning assumption is ongoing treatment, not a course you finish.

Last updated: September 2026. This article is for informational purposes only and does not constitute medical advice. Retatrutide is investigational and not approved by the FDA. Talk to a licensed clinician about starting, changing or stopping any weight management medication.