Guides / Side effects and results

GLP-1 weight loss by week: what the trials found

The trials report averages at set checkpoints, and the spread around each average is wide.

By PeptideTracker editorial team · Updated November 8, 2026 · 11 sources

[00] Short answer

  1. Semaglutide 2.4 mg (Wegovy): an average −10.6% by week 20 and −14.9% at week 68, vs −2.4% on placebo1,7.
  2. Tirzepatide (Zepbound) at week 72: −15.0% on 5 mg, −19.5% on 10 mg and −20.9% on 15 mg, vs −3.1% on placebo2.
  3. Orforglipron (Foundayo tablets) at week 72: −7.4% to −11.1%, vs −2.1% on placebo3.
  4. Results vary a lot. On Zepbound 15 mg, 56.7% lost at least a fifth of their weight, while 9.1% lost less than 5%2.
  5. People with type 2 diabetes lost less on every medicine. Wegovy 2.4 mg averaged −9.6% at 68 weeks in that trial1.

How much weight do you lose on a GLP-1 by week?

On semaglutide 2.4 mg, people lost an average of 10.6% of their body weight in the first 20 weeks and 14.9% by week 681,7. On tirzepatide 10 or 15 mg the average was 20.9% by week 369. Trials only weigh everyone at fixed checkpoints, so these are the points that have published numbers.

Average change in body weight at each checkpoint (adults without diabetes unless stated)
WhenMedicine and doseTrialAverage on the medicineAverage on placebo
Week 20Semaglutide 2.4 mg (Wegovy), after the dose stepsSTEP 4 start-up phase7−10.6%No placebo group
Week 36Tirzepatide 10 or 15 mg (Zepbound)SURMOUNT-4 start-up phase2,9−20.9%No placebo group
Week 64Semaglutide 25 mg tablet (Wegovy)Wegovy Study 71−13.6%−2.4%
Week 68Semaglutide 2.4 mg (Wegovy)STEP 11,4−14.9%−2.4%
Week 72Semaglutide 7.2 mg (Wegovy)Wegovy Study 81−18.8% (−15.5% on 2.4 mg)−3.9%
Week 72Tirzepatide 5 / 10 / 15 mg (Zepbound)SURMOUNT-12,5−15.0% / −19.5% / −20.9%−3.1%
Week 72Orforglipron 5.5 / 9 / 17.2 mg (Foundayo)ATTAIN-13,6−7.4% / −8.3% / −11.1%−2.1%
Week 88Tirzepatide 10 or 15 mg, kept goingSURMOUNT-49−25.3%−9.9% (stopped at week 36)
Week 104Semaglutide 2.4 mgSTEP 58−15.2%−2.6%
Week 176Tirzepatide 5 / 10 / 15 mg, people with prediabetesSURMOUNT-1, 3 years10−12.3% / −18.7% / −19.7%−1.3%
Week 208Semaglutide 2.4 mg, adults with heart diseaseSELECT11−10.2%−1.5%

The week 20 and week 36 numbers come from start-up phases where everyone took the medicine, and only count people who stayed on it. The SELECT and 3-year SURMOUNT-1 groups were different people from the main trials7,9–11.

The papers and labels can give slightly different numbers for the same trial, because they handle missing data differently. The ATTAIN-1 paper, for example, reports −7.5%, −8.4% and −11.2% on the trial's own dose names (6, 12 and 36 mg)6. The table uses the label numbers, which use Foundayo's dose names3.

Average weight loss with type 2 diabetes, per drug

People with type 2 diabetes lost less weight than people without it in every pair of trials. On Wegovy 2.4 mg the average was −9.6% at 68 weeks, compared with −14.9% in people without diabetes1.

Average change in body weight, adults with type 2 diabetes (US labels, section 14)
Medicine, dose and trial lengthOn the medicineOn placebo
Semaglutide 2.4 mg (Wegovy), 68 weeks1−9.6%−3.4%
Semaglutide 7.2 mg (Wegovy), 72 weeks1−13.2% (−10.4% on 2.4 mg)−3.8%
Tirzepatide 10 / 15 mg (Zepbound), 72 weeks2−12.8% / −14.7%−3.2%
Orforglipron 5.5 / 9 / 17.2 mg (Foundayo), 72 weeks3−5.1% / −7% / −9.6%−2.5%

The labels report this without giving a reason.

How much does GLP-1 weight loss vary from person to person?

A lot. On Zepbound 15 mg, 90.9% lost at least 5% of their weight and 56.7% lost at least 20%. That leaves 9.1% who lost less than 5%2. On Wegovy 2.4 mg, 83.5% reached 5% and 30.2% reached 20%1.

Percent of people who lost at least 5%, 10%, 15% or 20% of their weight (US labels, section 14)
Group5% or more10% or more15% or more20% or more
Wegovy 2.4 mg, 68 weeks183.5%66.1%47.9%30.2%
Wegovy placebo31.1%12%4.8%1.7%
Zepbound 5 mg, 72 weeks285.1%68.5%48.0%30.0%
Zepbound 15 mg, 72 weeks290.9%83.5%70.6%56.7%
Zepbound placebo34.5%18.8%8.8%3.1%
Foundayo 17.2 mg, 72 weeks371.5%54.5%35.9%18.4%
Foundayo placebo26.8%13%6%2.9%

The STEP 1 paper reports 86.4%, 69.1% and 50.5% reaching 5%, 10% and 15%, using a different analysis from the label4.

So an average of −15% includes people who lost a quarter of their weight and people who lost very little. Some people on placebo lost 10% or more too. The labels don't give a way to predict who will respond most.

Why your weight loss may not match the trial averages

Trial averages come from set dose schedules, set lifestyle programs and set groups of people. Your week-by-week numbers can differ for several reasons the labels describe.

  • The early weeks are low doses. Wegovy starts at 0.25 mg and reaches 2.4 mg in week 171. Zepbound starts at 2.5 mg for 4 weeks and goes up by 2.5 mg no sooner than every 4 weeks2. The Zepbound trials allowed up to 20 weeks to reach the assigned dose2.
  • Everyone had a diet and activity program. In the Zepbound and Wegovy trials, people were taught a diet of about 500 calories a day below their needs and were counseled to do at least 150 minutes of activity a week1–2.
  • Starting weight matters. In SELECT, people who started with a BMI under 30 lost a smaller percentage than people with a higher BMI11.
  • The averages include people who stopped. The main results count everyone who was randomized, including people who stopped taking the medicine4–5.
[Tool]See your label dose steps as datesThe planner lays out each step from your start date

Weight loss slowed and leveled off in the longer trials. The GLP-1 plateau guide covers when that happened and what happened when people stopped.

Questions

How much weight do you lose in the first month on a GLP-1?

The main trials don't publish a 4-week average. The earliest checkpoint we found was week 20, when people on semaglutide 2.4 mg had lost an average of 10.6% in the STEP 4 start-up phase.

How much weight do you lose on Wegovy in 3 months?

The trials we checked don't report a 12-week average. On semaglutide 2.4 mg, the average was 10.6% at week 20 in STEP 4 and 14.9% at week 68 in STEP 1.

How much weight do you lose on Zepbound in a year?

The SURMOUNT-1 trial reported results at 72 weeks, about 16.5 months: an average of 15.0% on 5 mg, 19.5% on 10 mg and 20.9% on 15 mg, vs 3.1% on placebo. In SURMOUNT-4, people on 10 or 15 mg had lost 20.9% by week 36.

Is Foundayo as effective as Zepbound or Wegovy?

In its 72-week trial, Foundayo averaged 7.4% to 11.1% weight loss vs 2.1% on placebo. These medicines haven't been compared head to head in the trials on this page, so the numbers can't be compared directly.

Why am I losing less than the trial average?

Averages hide a wide range. On Wegovy 2.4 mg, 16.5% of people lost less than 5% at 68 weeks. Dose steps, starting weight and type 2 diabetes all affected results in the trials. Your prescriber can review your progress.

Sources

Checked against Wegovy, Zepbound and Foundayo US prescribing information (2026, section 14), and the STEP 1, STEP 4, STEP 5, SELECT, SURMOUNT-1, SURMOUNT-4 and ATTAIN-1 papers on PubMed. How we check

  1. 1Wegovy (semaglutide) injection and tablets, US prescribing information, sections 2.2, 2.3 and 14.2. Novo Nordisk, revised 06/2026; Tables 8, 9, 11 and 12
  2. 2Zepbound (tirzepatide) US prescribing information, sections 2.1 and 14.1. Eli Lilly, revised 08/2026; Tables 2 and 6
  3. 3Foundayo (orforglipron) tablets, US prescribing information, sections 2.1 and 14. Eli Lilly, revised 07/2026; Table 6
  4. 4Wilding JPH, et al. Once-weekly semaglutide in adults with overweight or obesity (STEP 1). N Engl J Med 2021;384:989-1002. doi:10.1056/NEJMoa2032183; abstract
  5. 5Jastreboff AM, et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). N Engl J Med 2022;387:205-216. doi:10.1056/NEJMoa2206038; abstract
  6. 6Wharton S, et al. Orforglipron, an oral small-molecule GLP-1 receptor agonist for obesity treatment (ATTAIN-1). N Engl J Med 2025;393:1796-1806. doi:10.1056/NEJMoa2511774; abstract
  7. 7Rubino D, et al. Effect of continued weekly subcutaneous semaglutide vs placebo on weight loss maintenance (STEP 4). JAMA 2021;325:1414-1425. doi:10.1001/jama.2021.3224; abstract
  8. 8Garvey WT, et al. Two-year effects of semaglutide in adults with overweight or obesity: the STEP 5 trial. Nat Med 2022;28:2083-2091. doi:10.1038/s41591-022-02026-4; abstract
  9. 9Aronne LJ, et al. Continued treatment with tirzepatide for maintenance of weight reduction (SURMOUNT-4). JAMA 2024;331:38-48. doi:10.1001/jama.2023.24945; abstract
  10. 10Jastreboff AM, et al. Tirzepatide for obesity treatment and diabetes prevention (SURMOUNT-1, 3 years). N Engl J Med 2025;392:958-971. doi:10.1056/NEJMoa2410819; abstract
  11. 11Ryan DH, et al. Long-term weight loss effects of semaglutide in obesity without diabetes in the SELECT trial. Nat Med 2024;30:2049-2057. doi:10.1038/s41591-024-02996-7; results and discussion

This guide explains what labels and published studies say. It isn't medical advice and doesn't replace your prescriber or pharmacist.

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