GLP-1 Weight Loss: How Do I Compare With the Trials?
Enter your starting weight, current weight and start date, or load your weigh-ins. The calculator puts your course next to the published means from STEP 1 (semaglutide 2.4 mg) and SURMOUNT-1 (tirzepatide 5, 10 and 15 mg), each with placebo. It only shows values that appear as numbers in the sources.
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The calculation runs entirely on your device. No upload, no account and nothing stored on our server.
The calculator uses your trend weight from the start date on. The starting weight above stays the reference point.
Order and separators don't matter, comma or dot as decimal mark. Several weigh-ins on the same day are averaged.
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Apple Health (export.zip or export.xml), Withings (weight.csv or ZIP), Google Fit (Takeout CSV), Happy Scale, Libra, openScale, Trendcurve and any CSV with a date and a weight column.
Where you stand
- Not medical advice: the calculator compares numbers, it does not assess your treatment or your health.
- Trial means describe groups of hundreds of people over 68 or 72 weeks, with diet and activity counselling. Individual courses vary widely, in both directions.
- No dosing advice: your doctor decides on the dose and how it is increased. Do not change anything because of this comparison.
- The value used is the one for all randomised participants (treatment-policy or treatment-regimen estimand), including those who stopped treatment.
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The trial values at a glance
Mean change in body weight from baseline at the endpoint and share of participants with at least 5, 10, 15 and 20 percent weight loss.
| Arm | Week | Mean | Placebo | At least 5 / 10 / 15 / 20 % loss |
|---|---|---|---|---|
| Semaglutide 2.4 mg (STEP 1) | 68 | −14.9 % | −2.4 % | 86.4 % / 69.1 % / 50.5 % / 32.0 % Placebo: 31.5 % / 12.0 % / 4.9 % / 1.7 % |
| Tirzepatide 5 mg (SURMOUNT-1) | 72 | −15.0 % | −3.1 % | 85.1 % / 68.5 % / 48.0 % / 30.0 % Placebo: 34.5 % / 18.8 % / 8.8 % / 3.1 % |
| Tirzepatide 10 mg (SURMOUNT-1) | 72 | −19.5 % | −3.1 % | 88.9 % / 78.1 % / 66.6 % / 50.1 % Placebo: 34.5 % / 18.8 % / 8.8 % / 3.1 % |
| Tirzepatide 15 mg (SURMOUNT-1) | 72 | −20.9 % | −3.1 % | 90.9 % / 83.5 % / 70.6 % / 56.7 % Placebo: 34.5 % / 18.8 % / 8.8 % / 3.1 % |
STEP 1: 1,961 participants with a BMI of 30 or more (or 27 or more with a weight-related condition) without diabetes, mean baseline weight 105.3 kg. Shares: participants with data at week 68.
SURMOUNT-1: 2,539 participants with a BMI of 30 or more (or 27 or more with a weight-related condition) without diabetes, mean baseline weight 104.8 kg. Values from the US prescribing information (Study 1).
Sources
- Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med 2021;384:989-1002. doi.org/10.1056/NEJMoa2032183 · PubMed
- Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med 2022;387:205-216. doi.org/10.1056/NEJMoa2206038 · PubMed
- Wegovy (semaglutide) injection, US Prescribing Information, FDA 2021, Table 4. www.accessdata.fda.gov/drugsatfda_docs/nda/2021/215256Orig1s000Lbl.pdf
- Zepbound (tirzepatide) injection, US Prescribing Information, FDA 2023, Table 3 (Study 1 = SURMOUNT-1). www.accessdata.fda.gov/drugsatFDA_docs/label/2023/217806s000lbl.pdf
Track your course on GLP-1 in the app
Medication tracking in Trendcurve is free: enter your dose and injection day, every dose change adds a marker to your history, and a weekly reminder can be ticked off with "Done". With Pro the "Dose stages" card shows the period, trend change and weekly rate for each stage. No recommendations, not a medical device, and name and dose are never sent to analytics services.
What the trials show and what they don't
In STEP 1, adults with overweight or obesity without diabetes took semaglutide 2.4 mg or placebo once a week for 68 weeks, each in addition to diet and activity counselling. Body weight fell by 14.9 percent on average, with placebo by 2.4 percent.
In SURMOUNT-1, adults with obesity or overweight without diabetes received tirzepatide 5, 10 or 15 mg or placebo for 72 weeks. The mean loss was 15.0, 19.5 and 20.9 percent, with placebo 3.1 percent.
Both publications show the course over the weeks as a figure but give means as numbers only for the endpoint. This calculator therefore shows only start and endpoint as dots. A straight line between them would be too simple: it is dashed in the chart and labelled as interpolation.
How to use the comparison sensibly
- Compare percent, not kilos. The percentage scales with your starting weight.
- Use your trend weight instead of a single daily reading. Water and digestion shift the daily reading by one to two kilos.
- Before the endpoint the comparison says little. The trials report no verified intermediate values, and the dose was increased step by step in the first months.
- Even at the endpoint, a mean is not a benchmark for you. A large share of participants were well above or below it.
- Questions about effect, side effects and dose belong in a conversation with your doctor.