Plateau and rebound on AOM: what the evidence actually says.

1. Why "plateau" is a loaded word

The word plateau is doing a lot of work in obesity care. For the patient, it usually means "the scale stopped moving and I am worried the medication is failing". For the physician, it often means "the body has reached a new steady state, which is biologically expected". Most of the distress around plateau comes from this gap. Recognising what a plateau actually is, what it is not, and when it warrants a clinical decision is one of the most useful things a person on an anti-obesity medication can learn early.

Plateaus are normal. Trial-level weight curves are smooth at the population level, but individual curves are not. They include weeks of no movement, days of small regain, and stretches of slow loss that look very different on a kitchen scale than they do on a published graph.

2. Two plateaus that are normal on the journey

For most adults on weekly semaglutide or tirzepatide, two plateaus appear at predictable points.

The first plateau, around month 3 to 6, usually coincides with reaching the maintenance dose. Up to this point, weight loss has been driven by both the medication's effect on appetite and a body that was eating substantially more than it needed before. Once intake settles into the new pattern, the daily energy deficit narrows. Loss continues, but more slowly. This is not the medication failing; it is the medication doing what the package insert describes.

The second plateau, around month 12 to 18, is the steady state. The pivotal trials show that most weight loss occurs in the first 60 to 68 weeks of treatment, after which the curve flattens. In STEP-1, the mean loss at week 68 was 14.9% on semaglutide 2.4 mg vs 2.4% on placebo.⁵ In SURMOUNT-1, the mean loss at week 72 was 15.0% on tirzepatide 5 mg, 19.5% on 10 mg, and 20.9% on 15 mg, vs 3.1% on placebo.⁴ Past these timeframes, the question shifts from "how much more can I lose" to "how do I keep the result and protect the metabolic health that came with it".

3. Why the body resists weight loss

The biology of plateau is not a moral problem. It is a homeostatic one. Three mechanisms work in parallel:

• Reduced basal metabolic rate (BMR). A smaller body needs fewer calories at rest. A person who has lost 15 kg burns measurably fewer calories per day, even at the same activity level.
• Adaptive thermogenesis. Beyond the simple BMR drop, the body becomes more efficient at using energy during caloric deficit, partly through hormonal shifts (leptin down, ghrelin up, thyroid axis tone down).
• Lean mass loss. Between approximately 25% and 40% of weight lost on a GLP-1 medication is lean tissue, including muscle (around 25% in the SURMOUNT-1 body-composition substudy on tirzepatide;⁴ closer to 35-40% in the STEP-1 DXA substudy on semaglutide⁵). Less muscle means a lower resting metabolic rate, which compounds the first two effects.

None of this is unique to GLP-1 therapy; it is the same mechanism that has defeated diet-and-exercise programmes for decades. What is different on AOM is that the medication continues to suppress hunger signals, which keeps the deficit possible. Without that pharmacological help, the same biology drives most people back up the curve. This is the central finding of the discontinuation trials.

4. STEP-4: what happens when semaglutide is withdrawn

The STEP-4 trial, published in JAMA in 2021, was a randomised withdrawal study designed to answer one specific question: in adults with overweight or obesity who have already lost weight on semaglutide 2.4 mg, what happens if you stop?¹

The design was clean. After a 20-week run-in on semaglutide (mean loss 10.6%), 803 participants who had reached the 2.4 mg maintenance dose were randomised 2:1 to either continue semaglutide or switch to placebo for 48 more weeks, with lifestyle support in both arms. At week 68:

• Continued semaglutide: an additional 7.9% loss from the randomisation point.
• Switched to placebo: a 6.9% regain from the randomisation point.
• Treatment difference: 14.8 percentage points.

Other clinically relevant variables (waist circumference, systolic blood pressure, physical functioning) followed the same pattern: continued treatment improved them further; switching to placebo reverted most of the gains. The conclusion, in the authors' words, was that "maintaining treatment with semaglutide compared with switching to placebo resulted in continued weight loss".¹

5. SURMOUNT-4: the tirzepatide replication

SURMOUNT-4, published in JAMA in 2024, asked the same question of tirzepatide.² After a 36-week open-label lead-in on the maximum tolerated dose (10 or 15 mg, mean loss 20.9%), 670 participants were randomised 1:1 to continue tirzepatide or switch to placebo for 52 more weeks. At week 88:

• Continued tirzepatide: an additional 5.5% loss from the randomisation point. Total loss from baseline: 25.3%.
• Switched to placebo: a 14.0% regain from the randomisation point. Total loss from baseline: 9.9%.
• Treatment difference: 19.4 percentage points.
• Among those who continued, 89.5% maintained at least 80% of the lead-in weight loss; among those switched to placebo, only 16.6% did.²

The clinical signal is the same as STEP-4, with a magnitude that is, if anything, larger. The biology does not negotiate.

6. The STEP-1 extension: real-world withdrawal

The STEP-1 extension followed 327 participants for an additional 52 weeks after both treatment and lifestyle intervention were withdrawn at week 68. Mean weight loss was 17.3% on semaglutide at week 68. By week 120, one year off treatment, participants had regained 11.6 percentage points of body weight, leaving a net loss of only 5.6%. About two thirds of the original loss was gone, and most cardiometabolic improvements (blood pressure, HbA1c, C-reactive protein) reverted toward baseline.³

This is the most important sentence anyone considering a "break" from their medication should read: a year off semaglutide undid two thirds of a year of treatment, even with continued lifestyle effort. The medication was not a launch pad. It was a sustained intervention.

7. When a plateau warrants a clinical decision

Most plateaus are biology, not failure. A small number warrant a discussion with the prescribing physician. The signals to bring to the next consultation:

• A stall lasting more than 8 to 12 weeks at a sub-maintenance dose, where the question of whether titration upward is appropriate may be raised.
• A sustained regain of more than 5% from the lowest weight, especially if accompanied by a return of pre-treatment hunger patterns.
• Side effects that prevented titration to a therapeutic dose, in which case dose-extension strategies (holding a step longer, slower escalation) or a switch in molecule may be options.
• Very rapid loss with significant lean-mass loss (visible muscle decline, a fall in grip strength, fatigue): the rate of loss matters as much as the total loss.
• Significant social, psychological or eating-disorder signals emerging during the plateau period.

The decision tree from there belongs to the physician. Possible outcomes include continuing the current dose unchanged, escalating, switching molecule (semaglutide to tirzepatide or vice versa), adding a second agent, or, in rare cases, planning a structured tapering. None of these are simple, and none are reasonable to attempt alone.

8. The chronic-disease frame

The most useful reframing of plateau and rebound is also the most evidence-aligned: obesity is a chronic disease. Hypertension, type 2 diabetes, and dyslipidaemia are managed long term with medications that are taken for years, sometimes for life. Nobody asks a patient with hypertension whether they plan to "stop the medication once their blood pressure is normal", because everyone understands that the result is conditional on the treatment. The same logic applies, with the same evidence base, to anti-obesity medication.

The plateaus are real and biologically driven. The rebound on discontinuation is real and biologically driven. The implication is not that the medication failed; it is that the medication is doing chronic work, and the question is how to make that work sustainable: tolerability, daily structure, mental load, side-effect triage, and a clear conversation with the prescribing physician at each visit. We unpack the persistence side of this conversation in why half of GLP-1 patients stop in the first year.

9. What changes the trajectory

Boli Care exists because the medication works and the system around the medication does not. Between two consultations, the patient is alone with side effects, plateau questions, social pressure and a body that changes faster than identity. Boli is a Class I medical device that captures the structured information physicians need (graded side effects, dose history, eating rhythm, activity, mood) and presents it back at the next visit in a form that takes thirty seconds to read. Patients gain a daily rhythm and a place to put their questions. Physicians gain a clearer picture of how the treatment is actually being lived. The trajectory of persistence improves not because the medication changes, but because the information gap closes. Our 60-second orientation tool can help you decide whether Boli is the right fit.

References

1. Rubino D, Abrahamsson N, Davies M, et al. Effect of Continued Weekly Subcutaneous Semaglutide vs Placebo on Weight Loss Maintenance in Adults With Overweight or Obesity: The STEP 4 Randomized Clinical Trial. JAMA 2021;325(14):1414-1425. doi:10.1001/jama.2021.3224. PMID 33755728.
2. Aronne LJ, Sattar N, Horn DB, et al. Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial. JAMA 2024;331(1):38-48. doi:10.1001/jama.2023.24945. PMID 38078870.
3. Wilding JPH, Batterham RL, Davies M, et al. Weight regain and cardiometabolic effects after withdrawal of semaglutide: The STEP 1 trial extension. Diabetes, Obesity and Metabolism 2022;24(8):1553-1564. doi:10.1111/dom.14725. PMID 35441470.
4. Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine 2022;387(3):205-216. doi:10.1056/NEJMoa2206038. PMID 35658024.
5. Wilding JPH, Batterham RL, Calanna S, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine 2021;384(11):989-1002. doi:10.1056/NEJMoa2032183. PMID 33567185.