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Living with it

When weight loss on a GLP-1 slows down

Every weight-loss trial of these medicines has the same shape: a steep start, a long slope, and a line that eventually goes flat. A plateau is not a sign that something has gone wrong. Telling a real one from a noisy fortnight, though, takes a smoothed trend rather than a morning weigh-in.

By the Cafeity teamUpdated 6 min read

The short answer

Weight loss on a GLP-1 slows and eventually levels off for almost everyone. In the STEP 1 trial of semaglutide 2.4 mg, average weight fell from the first month, reached its lowest point around week 60, and held steady to week 68, at 14.9% below baseline on average.1 Day-to-day readings swing with water, salt and food, so a plateau is best judged on a smoothed trend over several weeks, and not in the weeks straight after a dose change. Whether and how treatment should change is a conversation with your prescriber.

Illustration over ten weeks: grey dots for daily weigh-ins scatter up and down by about a kilogram around a violet smoothed trend line that falls steadily and then flattens from week six, where the chart is shaded and labelled "trend flattens". Marked as an illustration, not real data.
An illustration, not real data. Daily weigh-ins (grey) bounce around the underlying trend (violet). Judging a plateau from any two dots is guesswork; the trend line is what flattens.

What the trials show

The large weight-management trials report averages, and the averages all flatten. In STEP 1, semaglutide 2.4 mg produced weight loss from the first assessment at week 4, reached its lowest point at week 60, and stabilised between weeks 60 and 68.1

Average change in body weight at the end of each trial. These are averages across hundreds of people — individual results varied widely, and none of them is a prediction for anyone.
TrialMedicine and doseLengthMedicinePlacebo
STEP 1Semaglutide 2.4 mg weekly68 weeks−14.9%−2.4%
SURMOUNT-1Tirzepatide 5 / 10 / 15 mg weekly72 weeks−15.0% / −19.5% / −20.9%−3.1%
Liraglutide label trialLiraglutide 3 mg daily56 weeks−8.4 kg (mean)−2.8 kg
Semaglutide tablet trialSemaglutide 25 mg daily tablet64 weeks−13.6%−2.4%
Orforglipron label trialOrforglipron daily tablet (highest dose)72 weeks−11.1%−2.1%

Sources: STEP 1, SURMOUNT-1, SCALE, and the semaglutide and orforglipron prescribing information.12345

Two things follow. A slowdown is built into how these medicines behave, not a sign they have stopped working. And the flat part comes after many months, not weeks — a fortnight without change in the second month is usually noise, not a plateau.

Why weight loss slows

Some of it is simple arithmetic. A smaller body needs less energy to run and to move, so the same eating produces a smaller deficit as weight comes off. Appetite changes on the medicine also settle once the dose is stable. And the body defends its weight in ways that are well documented in weight-loss research generally, not just with these medicines.

Some of it is the medicine's own timetable. Each dose takes weeks to reach a steady level — 4 to 5 weeks for weekly semaglutide, about 4 weeks for tirzepatide — so the effect of a dose increase unfolds gradually.67 A week or two of flat readings straight after a change says little either way.

A real plateau, or just noise?

Morning weight moves with water, salt, how much food is in the gut, bowel movements, hormones and last night's dinner. None of that is fat, and all of it can easily outweigh a week's real change. That is why Cafeity draws weight as a smoothed trend rather than a string of daily verdicts.

A useful rule of thumb before calling it a plateau:

  • Look at the trend, not the readings. A 7-day average, or a trend line, over at least three to four weeks.
  • Weigh consistently. Same time, same conditions — first thing in the morning after the toilet is the usual choice.
  • Discount the weeks after a dose change, while the new level is still building.
  • Check the other measures. Waist, how clothes fit, energy, food noise and blood pressure can keep moving while the scale does not.

What is worth raising with your prescriber

A genuine plateau is a normal point to review treatment with whoever prescribes it, and a record makes that conversation much easier. Things worth bringing:

  • Your smoothed weight trend over the last two to three months, with dose changes marked.
  • Roughly what and how much you are eating now, particularly protein.
  • Activity, including any strength training.
  • Sleep, alcohol and any new medicines.
  • Side effects, and whether they have changed what you can eat.

Guidance also sets expectations. In England, NICE's appraisals of semaglutide and tirzepatide for weight management ask prescribers to review treatment if less than 5% of starting weight has been lost after six months.89 The 2025 joint nutrition advisory emphasises adequate protein and regular strength training during treatment.10 What any of that means for your dose is your prescriber's call.

What not to do

  • Do not change the dose or the schedule on your own to break a plateau — not up, not down, not more often.
  • Do not cut food drastically. With a smaller appetite, very low intakes quickly mean too little protein and too few nutrients; the joint advisory flags the risk of nutrient shortfalls when intake falls below about 1,200 kcal a day for women and 1,800 for men.10 Cafeity will not set a calorie target below 1,200 kcal for this reason.
  • Do not judge it on a single week.

Keeping a record of it

Cafeity draws weight as a smoothed trend and says so on the chart — "based on your recent rate, not a prediction". Dose changes sit on the same timeline, so you can see whether a flat stretch is a plateau or simply the weeks after a step up, and bring the whole picture to your prescriber in the Visit Summary.

Cafeity weight screen showing a smoothed trend weight of 115.6 kg, down 5.5 kg since last week, with the note "Based on your recent rate. Not a prediction."
A smoothed trend, not a daily verdict.
Cafeity "Your week, understood" screen: Ora explains that everything is calculated from your own log, offers questions such as "When are my symptoms worst?", and shows the week's protein, energy, water, weight trend, symptom days and a note that protein was 80 g under target.
The week in sentences, built from your own log.

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Common questions

How long does a GLP-1 plateau last?
In the trials, average weight reached its lowest point and then held steady — in STEP 1 from about week 60 onwards.1 A plateau at that stage may be where weight settles on the current treatment. Earlier flat spells are often shorter and noisier; judge them on a trend over several weeks.
Does changing the injection site help a plateau?
The labels say it should not matter: semaglutide and tirzepatide reached similar exposure whether injected in the abdomen, thigh or upper arm.47 Rotating sites is recommended for skin reasons, not to change the effect.
Has my GLP-1 stopped working?
A slowdown is expected with every medicine in the class, so a flattening trend on its own does not mean that. Whether treatment should change is a question for your prescriber, ideally with a few months of your record in front of you.
Should I eat less to get past a plateau?
Be careful. On a reduced appetite, eating less quickly risks too little protein and too few nutrients.10 Talk to your prescriber or a dietitian before cutting further.

Sources

  1. Once-weekly semaglutide in adults with overweight or obesity (STEP 1) Wilding JPH et al. New England Journal of Medicine 2021;384:989–1002
  2. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1) Jastreboff AM et al. New England Journal of Medicine 2022;387:205–216
  3. A randomized, controlled trial of 3.0 mg of liraglutide in weight management (SCALE Obesity and Prediabetes) Pi-Sunyer X et al. New England Journal of Medicine 2015;373:11–22
  4. Semaglutide injection and tablets for weight management — US prescribing information DailyMed, US National Library of Medicine, version published 30 June 2026
  5. Orforglipron tablets for weight management — US prescribing information DailyMed, US National Library of Medicine, version published 13 August 2026
  6. Semaglutide injection for type 2 diabetes — US prescribing information DailyMed, US National Library of Medicine, version published 10 June 2026
  7. Tirzepatide injection for weight management and obstructive sleep apnoea — US prescribing information DailyMed, US National Library of Medicine, version published 2 September 2026
  8. Semaglutide for managing overweight and obesity (TA875) National Institute for Health and Care Excellence
  9. Tirzepatide for managing overweight and obesity (TA1026) National Institute for Health and Care Excellence
  10. Nutritional priorities to support GLP-1 therapy for obesity: a joint advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association and The Obesity Society Mozaffarian D et al. 2025 (published in four journals)

Written by the Cafeity team from the sources listed here. Figures from prescribing information are quoted as the label states them; trial results are averages from those trials, not predictions for any one person. This page has not yet been reviewed by a clinician — see the editorial policy for how pages are researched and corrected.