Clinical Evidence
Every trial behind every claim on this site
Quick read · 5 min
- •This page lists 47 clinical trials — the published research behind everything we say on this site.
- •17 trials for approved prescription drugs, 10 for future treatments still in development, and 20 for supplements.
- •Every row links to the original published study so you can check our sources yourself.
- •Click any trial to see a plain-English summary of what it found.
How to read this table
Phase tells you how far along a trial is. Phase 1 is early testing on small groups. Phase 2 tests a medium-sized group. Phase 3 is the large, definitive trial that regulators use to decide whether to approve a drug. Meta-analyses combine results from many trials to find the overall pattern.
Participants is the number of people in the study. Larger numbers generally give more reliable results. The biggest trial listed here (SELECT) studied over 17,000 people.
Duration matters because weight loss takes time. Short studies (under 6 months) may not show the full effect. The longest study here ran for 4 years.
Weight loss is always compared to a placebo (a dummy treatment). This means the number shows the drug's effect above and beyond what happens with lifestyle changes alone.
Showing 47 of 47 trials · Click any row to see the plain-English summary
| Treatment↕ | Trial↕ | Phase | Participants↕ | Duration↕ | Weight loss | Year↓ |
|---|---|---|---|---|---|---|
Retatrutide Future treatment | TRIUMPH-4 | Phase 3 | — | 68 weeks | 28.7% average weight loss at 12 mg — about 71 lbs on average | 2026 |
Tirzepatide Approved drug | SURMOUNT-5 | Phase 3 | — | 72 weeks | Tirzepatide was superior to semaglutide on weight loss and waist circumference | 2025 |
Orforglipron Future treatment | ATTAIN-1 | Phase 3 | — | 72 weeks | 12.4% at highest dose (36 mg daily pill) | 2025 |
Orforglipron Future treatment | ATTAIN-2 | Phase 3 | — | 72 weeks | 10.5% at highest dose (in people with type 2 diabetes) | 2025 |
Orforglipron Future treatment | ATTAIN-MAINTAIN | Phase 3 | — | 52 weeks | Maintained weight from prior injectable treatment (only 0.9 kg difference) | 2025 |
CagriSema Future treatment | REDEFINE 1 | Phase 3 | 3,417 | 68 weeks | 20.4% average (22.7% with full adherence) | 2025 |
CagriSema Future treatment | REDEFINE 2 | Phase 3 | 1,206 | 68 weeks | 13.7% average (15.7% with full adherence) | 2025 |
Probiotics Supplement | Meta-analysis of 27 RCTs (Nature Scientific Reports, 2025) | Meta-analysis | 1,938 | Varied (4–26 weeks) | 0.6–1.3 kg average weight loss; 0.5 cm waist circumference reduction | 2025 |
Tirzepatide Approved drug | SURMOUNT-3 | Phase 3 | — | 72 weeks | ~26% total from original baseline (18.4% additional after lifestyle phase) | 2024 |
Tirzepatide Approved drug | SURMOUNT-4 | Phase 3 | — | 88 weeks total (36-week lead-in + 52-week randomised phase) | 25.3% total over 88 weeks; 14% regain after stopping | 2024 |
Tirzepatide Approved drug | SURMOUNT-1 Body Composition Substudy | Phase 3 substudy | 160 | 72 weeks | 75% fat mass / 25% lean mass composition of weight lost | 2024 |
Semaglutide (oral pill) Approved drug | OASIS 4 | Phase 3 | 307 | 64 weeks | 13.6% average (16.6% with full adherence) | 2024 |
Amycretin (injection) Future treatment | Phase 1b/2a (subcutaneous) | Phase 1b/2a | — | 36 weeks | 22% at 20 mg weekly injection | 2024 |
Amycretin (oral pill) Future treatment | Phase 1 (oral formulation) | Phase 1 | — | 12 weeks | 13.1% in just 12 weeks (oral pill) | 2024 |
MariTide Future treatment | Phase 2 dose-finding study | Phase 2 | — | 52 weeks | Up to ~20% (non-diabetic); ~17% (with type 2 diabetes) | 2024 |
Saffron Extract Supplement | Satiereal RCT (2010) + 25-RCT meta-analysis (2024) | RCT + Meta-analysis | 60 | 8 weeks (RCT); varied (meta-analysis) | Reduced snacking frequency by 55% vs. placebo; approximately 2 kg average weight loss in meta-analysis | 2024 |
Myo-Inositol Supplement | JCEM PCOS Guidelines (2023) + Cardiometabolic meta-analysis (2024) | Meta-analysis | — | Varied (12–24 weeks) | Modest waist circumference and weight reduction in PCOS and insulin-resistant populations; 1–2 kg average | 2024 |
Semaglutide (injection) Approved drug | SELECT | Phase 3 (cardiovascular outcomes) | 17,604 | ~40 months (median) | 20% reduction in heart attacks, strokes, and cardiovascular death | 2023 |
Retatrutide Future treatment | Phase 2 RCT | Phase 2 | 338 | 48 weeks | 24.2% at highest dose (12 mg) — weight still dropping at 48 weeks | 2023 |
Psyllium Husk Supplement | Meta-analysis of 6 RCTs (overweight/obese only) | Meta-analysis | 354 | ~5 months (average) | 2.1 kg more than placebo (when taken before meals) | 2023 |
Spirulina Supplement | Network meta-analysis of 111 RCTs | Network meta-analysis | — | Varied | 1.77 kg more than placebo — HIGH certainty evidence | 2023 |
Chitosan Supplement | Network meta-analysis of 111 RCTs | Network meta-analysis | — | Varied | 1.70 kg more than placebo — moderate certainty | 2023 |
Nigella Sativa (Black Seed Oil) Supplement | Network meta-analysis of 111 RCTs | Network meta-analysis | — | Varied | 2.09 kg more than placebo — moderate certainty | 2023 |
Curcumin / Turmeric Supplement | Network meta-analysis of 111 RCTs | Network meta-analysis | — | Varied | 0.82 kg more than placebo — moderate certainty | 2023 |
Tirzepatide Approved drug | SURMOUNT-1 | Phase 3 | 2,539 | 72 weeks | 20.9% at highest dose (15 mg) | 2022 |
Semaglutide (injection) Approved drug | STEP 5 | Phase 3 | — | 104 weeks (2 years) | 15.2% sustained at 2 years | 2022 |
Semaglutide (injection) Approved drug | STEP 1 | Phase 3 | 1,961 | 68 weeks | 14.9% average weight loss | 2021 |
Semaglutide (injection) Approved drug | STEP 2 | Phase 3 | — | 68 weeks | 9.6% average weight loss (lower in people with diabetes) | 2021 |
Berberine Supplement | Meta-analysis of 12 RCTs | Meta-analysis | — | 8–12 weeks (most trials) | 2.07 kg more than placebo | 2020 |
Garcinia Cambogia Supplement | Meta-analysis of 8 RCTs | Meta-analysis | 530 | Varied | 1.34 kg — borderline significant, disappears in high-quality trials only | 2020 |
Caffeine Supplement | Meta-analysis of caffeine and weight loss | Meta-analysis | — | Short-term (varied) | 0.4–0.5 kg (short-term only; tolerance develops in 1–2 weeks) | 2017 |
Ashwagandha Supplement | Choudhary et al. RCT (2017) + Stress RCT (2012) | RCT | 52 | 8 weeks (Choudhary 2017); 60 days (2012 RCT) | About 3% body weight reduction vs. no change in placebo (in stressed adults only) | 2017 |
L-Carnitine Supplement | Meta-analysis of 9 RCTs | Meta-analysis | 911 | Varied | 1.33 kg more than placebo | 2016 |
Liraglutide Approved drug | SCALE Obesity and Prediabetes | Phase 3 | 3,731 | 56 weeks | 8.0% average weight loss | 2015 |
Liraglutide Approved drug | SCALE Diabetes | Phase 3 | — | 56 weeks | 6.0% in people with type 2 diabetes | 2015 |
Glucomannan (Konjac Fibre) Supplement | Meta-analysis of 8 RCTs | Meta-analysis | — | Varied | Not statistically significant (-0.22 kg, p>0.05) | 2014 |
Chromium Picolinate Supplement | Cochrane review of 9 RCTs | Cochrane review | 622 | Varied | 1.1 kg more than placebo — 'debatable clinical relevance' | 2013 |
Phentermine / Topiramate Approved drug | SEQUEL | Phase 3 extension | — | 108 weeks total (2 years) | Sustained weight loss with continued health improvements at 2 years | 2012 |
Green Tea Extract Supplement | Cochrane systematic review | Systematic review | — | Varied | 0.95 kg more than placebo — clinically insignificant | 2012 |
Conjugated Linoleic Acid (CLA) Supplement | Systematic review and meta-analysis | Meta-analysis | — | ~6 months (varied) | ~1.3 kg fat mass over 6 months — very modest | 2012 |
Protein Supplements Supplement | Meta-analysis of high-protein diets during energy restriction | Meta-analysis | — | Varied | Significantly greater fat loss and lean mass preservation vs standard protein | 2012 |
Phentermine / Topiramate Approved drug | CONQUER | Phase 3 | 2,487 | 56 weeks | 9.8% at full dose (15/92 mg) | 2011 |
Naltrexone / Bupropion Approved drug | COR-BMOD | Phase 3 | — | 56 weeks | 9.3% with drug + behaviour therapy (vs 5.1% placebo + therapy) | 2011 |
Naltrexone / Bupropion Approved drug | COR-I | Phase 3 | 1,742 | 56 weeks | 6.1% average weight loss | 2010 |
Orlistat Approved drug | XENDOS | Phase 3 | 3,305 | 4 years (208 weeks) | 2.8 kg more weight loss than placebo at 4 years | 2004 |
Orlistat OTC (Alli) Supplement | XENDOS (prescription-strength data) | Phase 3 (Rx-strength) | 3,305 | 4 years | 2.8 kg more than placebo at 4 years; 37% diabetes risk reduction | 2004 |
5-HTP Supplement | Cangiano et al. RCTs (1992 + 1998) | RCT | 20 | 5 weeks (1992); 8 weeks (1998) | About 1 kg per week vs 0.6 kg for placebo (1992 RCT); 4.6 kg vs 1.4 kg at 8 weeks (1998 RCT in diabetics) | 1998 |
How we select evidence
We prioritise the highest-quality evidence available for each treatment: large randomised controlled trials (studies where people are randomly assigned to get the real drug or a dummy pill), published in peer-reviewed medical journals.
For supplements, we rely on systematic reviews and meta-analyses — studies that combine results from many individual trials to find the overall pattern. Where a Cochrane review exists (considered the gold standard), we use that.
We never cite animal studies, case reports, or unpublished data as evidence for weight loss claims. If a treatment only has animal data (like raspberry ketones), we say so clearly.
Every source link goes to the original published study — not a news article or press release. Where the original study is behind a paywall, we link to the PubMed abstract instead.
Based on clinical trials · No rankings · Every claim linked to source
Last reviewed: March 2026