What the trial curves show
In both big weight trials, the average curve was steep at first, then flattened. In STEP 1, average weight did not reach its lowest point until week 60 (STEP 1, NEJM, 2021).
- Semaglutide 2.4 mg
- Placebo
Digitised from Figure 7 (STEP 1) of the Wegovy US label. Observed average change while in the trial. (Wegovy label, FDA, 2026). Points are read off the published chart, so they can be out by about a quarter of a percentage point. They are average results in the trial, not a prediction. Your results will differ.
Show the numbers
| Week | Semaglutide 2.4 mg | Placebo |
|---|---|---|
| 4 | −2.3% | −1.1% |
| 8 | −4.0% | −1.8% |
| 12 | −5.9% | −2.2% |
| 16 | −7.7% | −2.5% |
| 20 | −9.5% | −2.8% |
| 28 | −11.7% | −2.8% |
| 36 | −13.3% | −3.0% |
| 44 | −14.6% | −3.2% |
| 52 | −15.5% | −3.3% |
| 60 | −15.9% | −3.2% |
| 68 | −15.6% | −2.8% |
In SURMOUNT-1, the paper says the 5 mg group reached a plateau by week 72, and the 10 mg and 15 mg groups were close to one (SURMOUNT-1, NEJM, 2022).
Why it happens
A 2024 modelling study suggests plateaus happen because appetite rises as weight falls, until intake and needs meet again. It found semaglutide and tirzepatide weaken that appetite push-back, which is why weight keeps falling for longer, but it calls its results preliminary (Hall, Obesity, 2024).
The 6-month review
NICE and the labels build in a check. For tirzepatide, if less than 5% of your starting weight has been lost after 6 months on the highest dose you can tolerate, a decision is needed about whether to continue (NICE TA1026, 2024) (Mounjaro SmPC, MHRA, 2026). For semaglutide, NICE says to consider stopping if less than 5% has been lost after 6 months (NICE TA875, 2023).
That is a conversation with your prescriber, not a reason to change your dose yourself.
What to check before that conversation
Bring a short record, not just a feeling:
- How long you've been on your current dose.
- Your weekly weights over the last two months.
- Your waist and photos, because size can change when weight doesn't (more).
- Side effects, appetite and any missed doses.
- What you're eating, especially protein, and how active you are.
Before you call it a plateau.
- Count the weeks on this dose
- Average your weekly weights
- Check your waist and photos
- Note missed doses
- Bring the record to your prescriber
Where these facts come from.
- Wilding JPH et al. Once-weekly semaglutide in adults with overweight or obesity. N Engl J Med 2021;384:989-1002.
- Jastreboff AM et al. Tirzepatide once weekly for the treatment of obesity. N Engl J Med 2022;387:205-216.
- Hall KD. Physiology of the weight-loss plateau in response to diet restriction, GLP-1 receptor agonism, and bariatric surgery. Obesity 2024;32:1163-1168.
- WEGOVY (semaglutide) injection and tablets, US prescribing information, Novo Nordisk. Revised 6/2026. DailyMed.
- Tirzepatide for managing overweight and obesity. NICE technology appraisal guidance TA1026. Published 23 Dec 2024, updated 1 Sep 2025.
- Mounjaro KwikPen (tirzepatide) Summary of Product Characteristics. Revised 29 Aug 2026. emc.
- Semaglutide for managing overweight and obesity. NICE technology appraisal guidance TA875. Published 8 Mar 2023, updated 4 Sep 2023.
Checked 25 Oct 2026. Trial figures are average results in the trial, not predictions. Labels change; your prescriber and the leaflet in your pack have the current version.
Pip Body Scan is a personal progress record. It is not a medical device and does not give medical advice, diagnose conditions or recommend doses. Speak to your prescriber or another qualified healthcare professional about symptoms, side effects or changes to your treatment.