Clinical Evidence Reference
Tabular summary of clinical trial data for approved and pipeline anti-obesity medications. Designed as a quick reference for healthcare professionals.
Quick read · 8 min
This page presents the same data as our consumer pages but in a denser, tabular format suitable for clinical reference. All values are from published Phase 3 trial results. Weight loss percentages are mean placebo-subtracted unless otherwise noted. Source links are provided for every trial.
Approved medications — summary
| Drug | Form | Max weight loss | Key trial | Cost (list) |
|---|---|---|---|---|
| Tirzepatide Zepbound, Mounjaro | Once-weekly injection | 20.9% | SURMOUNT-1 | ~$1,086/month list price (LillyDirect savings programme: ~$650/month for eligible patients) |
| Semaglutide Wegovy injection, Wegovy pill, Ozempic | Injection: once-weekly · Pill: once-daily | 14.9% | STEP 1 | Pill: ~$149/month self-pay (~$25 with insurance). Injection: ~$1,350/month list price. Novo Nordisk NovoCare programme available. |
| Liraglutide Saxenda | Daily injection | 8% | SCALE Obesity and Prediabetes | Brand (Saxenda): ~$1,000–$1,349/month. Generic liraglutide (Teva, approved August 2025): typically $135–$200 less than brand. Check pharmacy pricing. |
| Phentermine / Topiramate ER Qsymia | Daily oral capsule — no injection | 9.8% | CONQUER | ~$30–$80/month generic; ~$200–$400/month brand (Qsymia) |
| Naltrexone / Bupropion ER Contrave | Twice-daily oral tablet — no injection | 9.3% | COR-I | ~$100–$400/month (brand). Generic available in some markets. |
| Orlistat Xenical | Three capsules daily, taken with each fat-containing meal | 8.5% | XENDOS | Rx ~$200–$400/month (Xenical); OTC ~$40–$60/month (Alli 60mg) |
| Orforglipron Foundayo | Once-daily pill — no injection, no fasting, no food timing | 12.4% | ATTAIN-1 | $149/month self-pay (lowest dose), up to $349/month (highest dose) via LillyDirect. $25/month with commercial insurance savings card. Medicare Part D ~$50/month expected from July 2026. Available since April 6, 2026. |
Detailed trial data — approved drugs
Tirzepatide
| Trial | Phase | N | Duration | Comparator | Weight loss | ≥5% | ≥20% | Source |
|---|---|---|---|---|---|---|---|---|
| SURMOUNT-1 | Phase 3 | 2,539 | 72 weeks | Placebo | 20.9% at highest dose (15 mg) | 89% | 50% | New England Journal of Medicine, 2022 |
| SURMOUNT-3 | Phase 3 | — | 72 weeks | Placebo (after lifestyle lead-in) | ~26% total from original baseline (18.4% additional after lifestyle phase) | — | — | Nature Medicine, 2024 |
| SURMOUNT-4 | Phase 3 | — | 88 weeks total (36-week lead-in + 52-week randomised phase) | Placebo (withdrawal study) | 25.3% total over 88 weeks; 14% regain after stopping | — | — | JAMA, 2024 |
| SURMOUNT-5 | Phase 3 | — | 72 weeks | Semaglutide 2.4 mg (head-to-head) | Tirzepatide was superior to semaglutide on weight loss and waist circumference | — | — | New England Journal of Medicine, 2025 |
| SURMOUNT-1 Body Composition Substudy | Phase 3 substudy | 160 | 72 weeks | Placebo | 75% fat mass / 25% lean mass composition of weight lost | — | — | Obesity, 2024 |
Semaglutide (injection)
| Trial | Phase | N | Duration | Comparator | Weight loss | ≥5% | ≥20% | Source |
|---|---|---|---|---|---|---|---|---|
| STEP 1 | Phase 3 | 1,961 | 68 weeks | Placebo | 14.9% average weight loss | 86% | — | New England Journal of Medicine, 2021 |
| STEP 2 | Phase 3 | — | 68 weeks | Placebo | 9.6% average weight loss (lower in people with diabetes) | — | — | New England Journal of Medicine, 2021 |
| STEP 5 | Phase 3 | — | 104 weeks (2 years) | Placebo | 15.2% sustained at 2 years | — | — | Nature Medicine, 2022 |
| OASIS 4 | Phase 3 | 307 | 64 weeks | Placebo | 13.6% average (16.6% with full adherence) | 76% | 33% | New England Journal of Medicine, 2024 |
| SELECT | Phase 3 (cardiovascular outcomes) | 17,604 | ~40 months (median) | Placebo | 20% reduction in heart attacks, strokes, and cardiovascular death | — | — | New England Journal of Medicine, 2023 |
| ORION | Indirect Comparison | — | 64–72 weeks | Cross-trial indirect comparison | Oral semaglutide showed ~3.2 percentage points more weight loss than orforglipron | — | — | Presented at Obesity Medicine Association (OMA) 2026, 2026 |
Liraglutide
| Trial | Phase | N | Duration | Comparator | Weight loss | ≥5% | ≥20% | Source |
|---|---|---|---|---|---|---|---|---|
| SCALE Obesity and Prediabetes | Phase 3 | 3,731 | 56 weeks | Placebo | 8.0% average weight loss | 63% | — | New England Journal of Medicine, 2015 |
| SCALE Diabetes | Phase 3 | — | 56 weeks | Placebo | 6.0% in people with type 2 diabetes | — | — | JAMA, 2015 |
Phentermine / Topiramate
| Trial | Phase | N | Duration | Comparator | Weight loss | ≥5% | ≥20% | Source |
|---|---|---|---|---|---|---|---|---|
| CONQUER | Phase 3 | 2,487 | 56 weeks | Placebo | 9.8% at full dose (15/92 mg) | 70% | — | The Lancet, 2011 |
| SEQUEL | Phase 3 extension | — | 108 weeks total (2 years) | Placebo | Sustained weight loss with continued health improvements at 2 years | — | — | American Journal of Clinical Nutrition, 2012 |
Naltrexone / Bupropion
| Trial | Phase | N | Duration | Comparator | Weight loss | ≥5% | ≥20% | Source |
|---|---|---|---|---|---|---|---|---|
| COR-I | Phase 3 | 1,742 | 56 weeks | Placebo | 6.1% average weight loss | 48% | — | The Lancet, 2010 |
| COR-BMOD | Phase 3 | — | 56 weeks | Placebo + intensive behaviour therapy | 9.3% with drug + behaviour therapy (vs 5.1% placebo + therapy) | — | — | Obesity, 2011 |
Orlistat
| Trial | Phase | N | Duration | Comparator | Weight loss | ≥5% | ≥20% | Source |
|---|---|---|---|---|---|---|---|---|
| XENDOS | Phase 3 | 3,305 | 4 years (208 weeks) | Placebo + lifestyle intervention | 2.8 kg more weight loss than placebo at 4 years | — | — | Diabetes Care, 2004 |
Orforglipron
| Trial | Phase | N | Duration | Comparator | Weight loss | ≥5% | ≥20% | Source |
|---|---|---|---|---|---|---|---|---|
| ATTAIN-1 | Phase 3 | — | 72 weeks | Placebo | 12.4% at highest dose (36 mg) | — | — | New England Journal of Medicine, 2025 |
| ACHIEVE-3 | Phase 3 | 1,698 | 52 weeks | Oral semaglutide 14mg (diabetes dose, not 25mg obesity dose) | 9.2% orforglipron vs 5.3% oral semaglutide (diabetes dose) | — | — | The Lancet, 2026 |
Pipeline drugs — trial data
These drugs are not yet FDA-approved. Trial data is from published results as of April 2026. Timelines are estimates.
| Drug | Trial | Phase | N | Duration | Weight loss | Source |
|---|---|---|---|---|---|---|
| Retatrutide | Phase 2 RCT | Phase 2 | 338 | 48 weeks | 24.2% at highest dose (12 mg) — weight still dropping at 48 weeks | New England Journal of Medicine, 2023 |
| Orforglipron | ATTAIN-1 | Phase 3 | — | 72 weeks | 12.4% at highest dose (36 mg daily pill) | New England Journal of Medicine, 2025 |
| Orforglipron | ATTAIN-2 | Phase 3 | — | 72 weeks | 10.5% at highest dose (in people with type 2 diabetes) | The Lancet, 2025 |
| Orforglipron | ATTAIN-MAINTAIN | Phase 3 | — | 52 weeks | Maintained weight from prior injectable treatment (only 0.9 kg difference) | Eli Lilly press release, 2025 |
| CagriSema | REDEFINE 1 | Phase 3 | 3,417 | 68 weeks | 20.4% average (22.7% with full adherence) | New England Journal of Medicine, 2025 |
| CagriSema | REDEFINE 2 | Phase 3 | 1,206 | 68 weeks | 13.7% average (15.7% with full adherence) | New England Journal of Medicine, 2025 |
| Amycretin (injection) | Phase 1b/2a (subcutaneous) | Phase 1b/2a | — | 36 weeks | 22% at 20 mg weekly injection | Presented at EASD 2024, 2024 |
| Amycretin (oral pill) | Phase 1 (oral formulation) | Phase 1 | — | 12 weeks | 13.1% in just 12 weeks (oral pill) | EASD 2024 annual meeting, 2024 |
| MariTide | Phase 2 dose-finding study | Phase 2 | — | 52 weeks | Up to ~20% (non-diabetic); ~17% (with type 2 diabetes) | Nature Medicine, 2024 |
| Retatrutide | TRIUMPH-4 | Phase 3 | — | 68 weeks | 28.7% average weight loss at 12 mg — about 71 lbs on average | Eli Lilly press release, 2026 |
GI side effect rates — approved GLP-1 drugs
From pivotal trial data. Rates are for the highest approved dose vs placebo.
| Side effect | Tirzepatide | Semaglutide | Liraglutide | Phentermine / Topiramate ER | Naltrexone / Bupropion ER | Orlistat | Orforglipron |
|---|---|---|---|---|---|---|---|
| Nausea | 31% | 44% | 40% | — | 33% | — | 33% |
| Diarrhoea | 23% | 30% | 21% | — | — | — | 15% |
| Vomiting | 18% | 24% | 16% | — | 11% | — | 19% |
| Constipation | 12% | 24% | 19% | 17% | 19% | — | 18% |
About this reference
This page is designed as a quick clinical reference, not a comprehensive review. All data is sourced from published peer-reviewed trials and FDA prescribing information. Weight loss figures are mean values from the primary efficacy endpoints of each trial. Individual patient results vary. For prescribing decisions, consult the full prescribing information for each medication.
Plain Decisions is a consumer health information site. We are not a medical practice and do not provide clinical recommendations.
Based on clinical trials · No rankings · Every claim linked to source
Last reviewed: April 2026
Medical disclaimer: This website is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any treatment.