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D2C Peptides

Research goal

GLP-1 and weight loss

In large placebo-controlled trials lasting 68 to 72 weeks, adults lost an average of 14.9% of body weight on semaglutide 2.4 mg and up to 20.9% on tirzepatide, against 2.4% and 3.1% on placebo.12 Much of the lost weight returned after treatment stopped.38 This page reports what trials and labels show, and it makes no promise.

This page summarizes published sources for information only. It is not medical advice and does not tell anyone to use a product. Questions about your own health belong with a licensed clinician. For questions about an order or a product, contact us.

What sources report

The results below come from randomized trials of approved medicines and of investigational retatrutide. Each figure is the average change in body weight from the start of the trial, set beside placebo.

Approved medicines in adults without diabetes

Trial or label study Medicine and dose Length Average weight change Placebo
STEP 1 (double-blind, 1,961 adults) Semaglutide 2.4 mg weekly 68 weeks -14.9%1 -2.4%1
Wegovy label, adults with obesity Semaglutide 7.2 mg weekly (2.4 mg arm: -15.5%) 72 weeks -18.8%4 -3.9%4
Wegovy label, Study 7 Semaglutide 25 mg daily tablet 64 weeks -13.6%4 -2.4%4
SURMOUNT-1 (phase 3, 2,539 adults) Tirzepatide 5, 10 or 15 mg weekly 72 weeks -15.0%, -19.5% and -20.9%2 -3.1%2

In STEP 1, stopping treatment because of stomach and bowel events happened in 4.5% on semaglutide, against 0.8% on placebo.1 The full list of reported effects is on GLP-1 side effects.

Head-to-head trials

  • STEP 8 (phase 3b, open-label, 338 adults, 68 weeks): weight changed -15.8% on weekly semaglutide 2.4 mg and -6.4% on daily liraglutide 3.0 mg.5
  • SURMOUNT-5 (phase 3b, 751 adults, 72 weeks): weight changed -20.2% on tirzepatide and -13.7% on semaglutide, each at the highest dose people tolerated.6

Adults with type 2 diabetes

Average losses in these trials were smaller than in the trials of people without diabetes above.41311

  • Wegovy label: -13.2% on 7.2 mg and -10.4% on 2.4 mg, against -3.8% on placebo, at 72 weeks.4
  • Zepbound label, Study 2 (BMI 27 or more, 72 weeks): -12.8% on 10 mg and -14.7% on 15 mg, against -3.2% on placebo.13
  • TRIUMPH-2 (retatrutide, phase 3, 1,152 adults, 80 weeks): -11.9% to -18.8% across the 4 to 12 mg doses, against -5.1% on placebo.11

Investigational: retatrutide

  • Phase 2 (338 adults, 48 weeks): -24.2% on 12 mg, against -2.1% on placebo.9 On 12 mg, 83% lost at least 15% of body weight, against 2% on placebo.9
  • TRIUMPH-1 (phase 3, 2,339 adults without diabetes, 80 weeks): -17.6%, -23.7% and -25.0% on 4, 9 and 12 mg, against -3.9% on placebo.10

No regulator, FDA included, has approved retatrutide.12 These results come from Lilly's drug under trial conditions and do not describe retatrutide products from outside the trials.1012

After treatment stops

  • STEP 4 (phase 3a): in a 20-week run-in, 902 adults lost 10.6% on average on semaglutide.7 Of the 803 then randomized, those who stayed on it lost a further 7.9% by week 68.7 Those switched to placebo regained 6.9%.7
  • STEP 1 extension (327 adults): treatment ended at week 68.3 By week 120, net change from the start was -5.6% in the former semaglutide group and -0.1% in the former placebo group.3 Improvements in heart and metabolic risk markers drifted back toward baseline.3
  • SURMOUNT-4 (670 adults): the authors concluded that withdrawing tirzepatide led to substantial regain, while continued treatment kept the loss and added to it.8
  • SURMOUNT-1, three years (1,032 adults with prediabetes, still on treatment): weight change at 176 weeks was -12.3% to -19.7% on tirzepatide.20 It was -1.3% on placebo.20

What the label says

Four GLP-1 brands carry FDA weight-reduction labels: Wegovy (injection and tablets), Zepbound, Saxenda and Foundayo.4131415 The Wegovy, Zepbound and Foundayo labels cover adults with obesity, or with overweight plus at least one weight-related condition.41315 All four labels pair the drug with a reduced-calorie diet and more physical activity.4131415 Wegovy injection also covers children 12 and older with obesity.4 Saxenda covers children 12 and older with obesity who weigh more than 60 kg.14

Ozempic and Mounjaro share their active ingredients with Wegovy and Zepbound, but their labels cover type 2 diabetes uses.1617 The prescriber sets the dose within each label's steps, and GLP-1 dosage lays out every schedule. The Wegovy, Zepbound and Foundayo labels also carry the class boxed warning on thyroid C-cell tumors.41315

What is and is not known

Trial averages describe groups, not any one person. The longest weight follow-ups summarized here run about three years for tirzepatide and 120 weeks for semaglutide.203 Retatrutide's longest published trials ran 80 weeks.1011

None of these trials used research-labeled products. FDA says research-labeled GLP-1 products sold to consumers are of unknown quality and may be harmful.18 In a 2026 laboratory test, three vials sold in Australia as retatrutide 10 mg held 5.13 mg, 16.5 mg and 19.0 mg.19 That is 51% to 190% of the labeled amount.19 Sterility and endotoxin were not tested.19

What is GLP-1? explains the class, GLP-1 dosage gives the label schedules and GLP-1 side effects lists what trials and labels report. Single-compound pages cover semaglutide and weight loss, tirzepatide and weight loss, Wegovy and weight loss and Mounjaro and weight loss. Other compounds people search for this goal are on Peptides and weight loss.

Read next

More goal pages

Frequently asked questions

How much weight do people lose on GLP-1 medicines?

Results vary widely between people.113 In STEP 1, 86.4% of adults on semaglutide 2.4 mg lost at least 5% of body weight.1 At least 10% was lost by 69.1%, and at least 15% by 50.5%.1 On placebo the figures were 31.5%, 12.0% and 4.9%.1 In SURMOUNT-1, 30.0% to 56.7% of adults on tirzepatide lost 20% or more, against 3.1% on placebo.13

How long does it take to lose 20 pounds on a GLP-1?

Trials report percent change over a year or more, not the time needed to lose a set number of pounds. Dose increases alone take months: Wegovy injection reaches its maintenance dose at week 17, and SURMOUNT-1 used a 20-week escalation period.42 The main results were measured at 68 to 72 weeks.12 A trial average cannot predict one person's pace.

What happens when you stop taking a GLP-1?

Weight tends to come back.38 One year after semaglutide was stopped in the STEP 1 extension, people had regained about two-thirds of the weight they had lost.3 In SURMOUNT-4, adults who switched from tirzepatide to placebo after 36 weeks regained 14.0% of body weight over the next 52 weeks.8 Those who stayed on tirzepatide lost a further 5.5%.8

Will a GLP-1 get rid of belly fat?

The closest measure these trials report is waist size. In SURMOUNT-1, waist circumference fell 14.0 to 18.5 cm across tirzepatide doses, against 4.0 cm on placebo.13 In SURMOUNT-5 it fell 18.4 cm on tirzepatide and 13.0 cm on semaglutide over 72 weeks.6 Both the Wegovy and Zepbound labels report that fat mass falls more than lean mass.413

Written by D2C Peptides Editorial Team.

Pending qualified review.

Updated .

Sources

  1. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1; Wilding et al.), PubMed abstract PMID 33567185. New England Journal of Medicine (abstract via NLM PubMed E-utilities), 2021.
  2. Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med 2022;387(3):205-216. PMID 35658024, doi:10.1056/NEJMoa2206038 (PubMed record). New England Journal of Medicine (record via NCBI PubMed E-utilities), 2022.
  3. Weight regain and cardiometabolic effects after withdrawal of semaglutide: The STEP 1 trial extension (Wilding et al.), PubMed abstract PMID 35441470. Diabetes, Obesity and Metabolism (abstract via NLM PubMed E-utilities), 2022.
  4. WEGOVY (semaglutide) injection and tablets, prescribing information (revised 6/2026). U.S. National Library of Medicine, DailyMed (label by Novo Nordisk), 2026.
  5. Effect of Weekly Subcutaneous Semaglutide vs Daily Liraglutide on Body Weight in Adults With Overweight or Obesity Without Diabetes (STEP 8; Rubino et al.), PubMed abstract PMID 35015037. JAMA (abstract via NLM PubMed E-utilities), 2022.
  6. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity (SURMOUNT-5; Aronne et al.), PubMed abstract PMID 40353578. New England Journal of Medicine (abstract via NLM PubMed E-utilities), 2025.
  7. Effect of Continued Weekly Subcutaneous Semaglutide vs Placebo on Weight Loss Maintenance (STEP 4; Rubino et al.), PubMed abstract PMID 33755728. JAMA (abstract via NLM PubMed E-utilities), 2021.
  8. Aronne LJ et al. Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial. JAMA 2024;331(1):38-48. PMID 38078870, doi:10.1001/jama.2023.24945 (PubMed record). JAMA (record via NCBI PubMed E-utilities), 2024.
  9. Triple-Hormone-Receptor Agonist Retatrutide for Obesity: A Phase 2 Trial. New England Journal of Medicine (PubMed record, National Library of Medicine), 2023.
  10. Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity (TRIUMPH-1). New England Journal of Medicine (PubMed record, National Library of Medicine), 2026.
  11. Retatrutide in adults with obesity and type 2 diabetes (TRIUMPH-2): a double-blind, parallel-group, randomised, placebo-controlled, phase 3 trial. The Lancet (PubMed record, National Library of Medicine), 2026.
  12. Is retatrutide available in the consumer market? (Lilly Medical answer, last reviewed August 4, 2026). Eli Lilly and Company (Lilly Medical), 2026.
  13. ZEPBOUND (tirzepatide) injection, prescribing information (revised 8/2026). U.S. National Library of Medicine, DailyMed (label by Eli Lilly), 2026.
  14. SAXENDA (liraglutide) injection, prescribing information (revised 6/2026). U.S. National Library of Medicine, DailyMed (label by Novo Nordisk), 2026.
  15. FOUNDAYO (orforglipron) tablets, prescribing information (revised 7/2026). U.S. National Library of Medicine, DailyMed (label by Eli Lilly), 2026.
  16. OZEMPIC (semaglutide) injection, prescribing information (revised 5/2026). U.S. National Library of Medicine, DailyMed (label by Novo Nordisk), 2026.
  17. MOUNJARO (tirzepatide) injection, prescribing information (revised 8/2026). U.S. National Library of Medicine, DailyMed (label by Eli Lilly), 2026.
  18. FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss. U.S. Food and Drug Administration, 2026.
  19. Composition and Labelling Accuracy of Products Sold as Retatrutide in Australia. Drug and Alcohol Review (PubMed Central full text), 2026.
  20. Jastreboff AM et al. Tirzepatide for Obesity Treatment and Diabetes Prevention (SURMOUNT-1, 3-year). N Engl J Med 2025;392(10):958-971. PMID 39536238, doi:10.1056/NEJMoa2410819 (PubMed record). New England Journal of Medicine (record via NCBI PubMed E-utilities), 2025.