In short: In the large trials, weight on semaglutide 2.4 mg fell by a mean of 10.6 percent in the first 20 weeks, a little over 0.5 percent per week. After that the curve flattens: after 68 weeks the mean was 14.9 percent. On tirzepatide the mean was 20.9 percent after 36 weeks. Starting at 220 lb (100 kg), that means roughly 1.1 lb (0.5 kg) per week at first and clearly less later. Your own single week can be far above or below that.
These numbers are trial averages, not a prediction for you. They do help you place your own curve: is a week with 0.4 lb too little? Is a month with 9 lb too much? This article shows the trial curve week by week and how to read your weekly rate against it. Trendcurve is not a medical device and gives no advice on dose or administration.
The curve in numbers: what the trials measured
The trials show a fast stretch in the first five to nine months and a much flatter curve afterwards. These four results are published and can be converted to a weekly average:
| Trial | Drug | Period | Mean loss | Average per week | Starting at 220 lb (100 kg) |
|---|---|---|---|---|---|
| STEP 4, run-in | Semaglutide up to 2.4 mg | Weeks 0 to 20 | 10.6% | 0.53% | about 1.2 lb (0.53 kg) |
| STEP 1 | Semaglutide 2.4 mg | Weeks 0 to 68 | 14.9% | 0.22% | about 0.5 lb (0.22 kg) |
| SURMOUNT-4, lead-in | Tirzepatide 10 or 15 mg | Weeks 0 to 36 | 20.9% | 0.58% | about 1.3 lb (0.58 kg) |
| SURMOUNT-1 | Tirzepatide 5 / 10 / 15 mg | Weeks 0 to 72 | 15.0 / 19.5 / 20.9% | 0.21 / 0.27 / 0.29% | about 0.5 to 0.6 lb (0.21 to 0.29 kg) |
The weekly values are simple averages over the whole period, not the rate of one particular week. That they are higher over 20 or 36 weeks than over 68 or 72 weeks shows the shape of the curve: faster at the start, flatter towards the end. Two caveats apply. STEP 4 and SURMOUNT-4 only count participants who completed the run-in, which makes those numbers look rather favourable. And the placebo groups in STEP 1 and SURMOUNT-1 also lost 2.4 and 3.1 percent with diet and exercise counselling.
Week by week: three stretches of the curve
The typical curve on a GLP-1 injection has three stretches: a slow start, a fast middle and a flat end.
Weeks 1 to 4: starting on a low dose. In the trials, treatment began at the lowest dose. Appetite often drops early, but the scale shows a mix of water and fat. The trials give no separate number for this stretch. A pound up or down in one week says little here.
Roughly weeks 5 to 20 or 36: the fast stretch. Most of the loss happens in this period. On average that is a little over 0.5 percent of body weight per week, with flat weeks and sudden drops in between.
After that: the curve flattens. The longer the treatment runs, the slower the rate. As a rough comparison: in STEP 4 the mean was already 10.6 percent after 20 weeks, in STEP 1 it was 14.9 percent after 68 weeks. So the larger part of the loss falls into the first months. That is not failure but the normal shape: with every pound you lose, your energy needs fall too.
Worked example: what it means for your scale
Percentages are fair, pounds are tangible. Convert the trial values to your starting weight:
| Starting weight | 0.5% per week (fast stretch) | 0.22% per week (average over 68 weeks) | 14.9% after 68 weeks |
|---|---|---|---|
| 176 lb (80 kg) | 0.9 lb (0.40 kg) | 0.4 lb (0.18 kg) | 26 lb (11.9 kg) |
| 220 lb (100 kg) | 1.1 lb (0.50 kg) | 0.5 lb (0.22 kg) | 33 lb (14.9 kg) |
| 265 lb (120 kg) | 1.3 lb (0.60 kg) | 0.6 lb (0.26 kg) | 39 lb (17.9 kg) |
At 220 lb, about 1 lb per week in the fast stretch is within the trial range, and about 0.5 lb per week after a year is too. Trendcurve shows a warning if your measured rate is above 1 percent of body weight per week. That is a reason to talk to your doctor, not a reason to change anything yourself.
When is the dose increased?
Whether and when your dose goes up is your doctor's decision, based among other things on tolerability, effect and the prescribing information. In the trials the dose was raised by a fixed protocol in four-week steps: in STEP 4 it took 16 weeks to reach the target dose. In everyday care the pace can differ, for example if side effects occur.
For your curve this means: a slow week is not a signal to change the dose. A more useful question is how fast your trend is moving on the current step. You can take that number to your next appointment. How to read dose steps in your curve is covered in Semaglutide weight loss timeline: what a normal curve looks like.
What happens after stopping
After stopping, weight went back up substantially on average in the trials. In STEP 4, participants who switched to placebo after 20 weeks regained a mean of 6.9 percent by week 68, while those who stayed on semaglutide lost another 7.9 percent. In SURMOUNT-4, switching to placebo led to a mean regain of 14.0 percent, while tirzepatide led to a further 5.5 percent loss.
A maintenance corridor around your goal weight helps you see a rise early in your trend instead of months later on the scale. Whether to continue or stop is a decision you make with your doctor.
How to compare your own curve
Compare your own curve as a trend against the trial curve, not week by week. Three steps:
- Make your weight curve with the weight loss graph maker. It shows your trend and weekly rate in pounds or kilograms and in percent.
- Put your progress next to the means from STEP 1 and SURMOUNT-1 in the GLP-1 trial comparison, with placebo, proportions and sources.
- Judge a dose step only after two to four weeks of regular weigh-ins.
In the Trendcurve app the medication companion is free: every dose change sets a marker, and a weekly reminder for injection day can be ticked off. With Pro, the Dose steps card shows the weekly rate per step. Name and dose stay on your device.
Frequently asked questions
How much weight do you lose per week on GLP-1?
In the trials, on average about 0.5 to 0.6 percent of body weight per week in the first 20 to 36 weeks, and 0.2 to 0.3 percent per week when averaged over the full 68 to 72 weeks. Starting at 220 lb (100 kg), that is roughly 1.1 lb (0.5 kg) per week at first. Single weeks vary a lot.
What is the average weight loss with GLP-1 agonists?
In STEP 1, semaglutide 2.4 mg led to a mean loss of 14.9 percent after 68 weeks (placebo 2.4 percent). In SURMOUNT-1, tirzepatide led to 15.0, 19.5 and 20.9 percent after 72 weeks at 5, 10 and 15 mg (placebo 3.1 percent). These are averages, not predictions for one person.
When should a GLP-1 dose be increased?
Your doctor decides that, based among other things on how well you tolerate it and how it works for you. In the trials the dose was raised in four-week steps by a fixed protocol. A slow week on the scale is not a reason to change your dose yourself.
Is it normal not to lose weight for a week on GLP-1?
Yes. Water, salt and digestion shift your daily reading by 1 lb or more. What matters is the weekly rate of your trend over at least two to four weeks, not the difference between two weigh-ins.