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Best Peptides for Fat Loss: Evidence-Based Roundup

Ranked roundup of peptides studied for fat loss — GLP-1 / GIP agonists, GH-axis fragments, and supporting metabolic peptides — with mechanism, evidence quality, and how to choose.

Published Jun 14, 20266 min read

The peptides with the strongest fat-loss evidence are the GLP-1 / GIP / glucagon agonists (Semaglutide, Tirzepatide, Retatrutide, Cagrilintide). They produce 15–24% mean body-weight reduction in trials, most of which is fat mass. The GH-axis fragments (AOD-9604, HGH Fragment 176-191) and metabolic peptides (MOTS-c, AICAR, BAM-15) appear repeatedly in fat-loss discussions but have weaker direct evidence. This roundup ranks the major options by evidence strength.

For the underlying mechanism, trial data, and side-effect profiles, see the pillar at peptides for weight loss. For the full hub of weight-loss peptides ranked by study count, see /peptides/category/weight-loss.

How we rank

Three factors:

  1. Evidence quality. Phase 3 FDA-approved > Phase 3 trials in progress > Phase 2 trials > observational > animal-only > anecdote.
  2. Effect size. Mean % body-weight reduction in the best-available trial at maintenance dose.
  3. Safety/tolerability. Trial discontinuation rate; severity profile of common side effects.

We do not rank by accessibility, cost, or sourcing — those depend on individual circumstances.

Tier 1 — Strong evidence (FDA-approved + Phase 3 reads)

1. Tirzepatide (Mounjaro / Zepbound)

GIP + GLP-1 dual agonist. SURMOUNT-1 Phase 3 trial: ~21% mean body-weight reduction at 72 weeks at the 15 mg weekly dose. Currently the largest trial weight-loss effect among FDA-approved drugs.

Approved for type 2 diabetes (Mounjaro) and chronic weight management (Zepbound). Once-weekly SC injection. Side-effect profile dominated by GI (nausea, vomiting, diarrhea), generally milder than Semaglutide at matched-efficacy doses.

Tirzepatide research profile.

2. Semaglutide (Ozempic / Wegovy)

GLP-1 monoagonist. STEP-1 Phase 3 trial: ~15% mean body-weight reduction at 68 weeks at the 2.4 mg weekly dose. Largest cardiovascular-outcome evidence (SELECT trial: 20% relative reduction in MACE).

Approved for type 2 diabetes (Ozempic) and chronic weight management (Wegovy). Once-weekly SC injection. Longest track record in the modern GLP-1 wave.

Semaglutide research profile.

3. Retatrutide (LY3437943)

GLP-1 + GIP + glucagon triple agonist. Phase 2 data: ~24% mean body-weight reduction at 48 weeks at the 12 mg weekly dose — the largest mean effect of any weight-loss drug in modern trials. Phase 3 trials ongoing.

The glucagon-receptor component adds energy expenditure to the appetite-suppression mechanism, which is the leading hypothesis for the larger numbers. Final safety picture awaits Phase 3 reads.

Retatrutide research profile.

Tier 2 — Emerging evidence (Phase 3 in progress / approved for specific indications)

4. Cagrilintide (and CagriSema)

Long-acting amylin receptor agonist. Cagrilintide alone produces ~10% weight loss at maintenance. The CagriSema combination (Cagrilintide + Semaglutide) in Phase 3 trials has produced 15–22% depending on cohort and dose — a different-mechanism complement to GLP-1 that does not duplicate the GLP-1 side-effect profile.

Cagrilintide research profile.

5. Survodutide (BI 456906)

GLP-1 + glucagon dual agonist. Phase 2 SYNCHRONIZE: ~19% weight loss at 46 weeks. Phase 3 in progress.

Survodutide research profile.

6. Mazdutide (IBI362)

GLP-1 + glucagon dual agonist. Phase 3 trial results from China: ~15% weight loss at 48 weeks. Similar mechanism class to Survodutide.

Mazdutide research profile.

7. Orforglipron (LY-3502970)

Oral small-molecule GLP-1 receptor agonist (not a peptide structurally, but works on the same receptor). Phase 3 ATTAIN: ~14% weight loss at 36 weeks at the highest dose. Oral dosing expands the addressable population significantly. FDA decision expected in 2026.

Orforglipron research profile.

8. Tesamorelin (Egrifta)

GHRH analog, FDA-approved for HIV-associated lipodystrophy (visceral fat reduction). The on-label data is specifically visceral adipose tissue reduction, not whole-body weight loss; the visceral effect is meaningful. Off-label use for body-composition purposes is widespread; clinical evidence outside the lipodystrophy indication is weaker.

Tesamorelin research profile.

Tier 3 — Weak direct evidence (anecdote-dominated)

9. AOD-9604

A fragment of growth hormone (residues 176-191) marketed as a fat-loss peptide. Small studies in the 2000s showed minimal or no weight loss vs placebo at the doses tested. Persists in informal "fat loss stack" recommendations despite the weak evidence; the realistic effect at typical doses is small.

AOD-9604 research profile.

10. HGH Fragment 176-191

Same fragment as AOD-9604 marketed under a different name. Same evidence profile (weak direct human data).

HGH Fragment 176-191 research profile.

11. MOTS-c

Mitochondrial-derived peptide. Animal-data signal for metabolic improvement and improved exercise capacity; human data limited. Sometimes added to stacks for general metabolic-health support rather than as a primary fat-loss agent.

MOTS-c research profile.

12. AICAR (Acadesine)

AMPK activator. Animal data shows increased fatty-acid oxidation. Human use is limited and primarily in research settings; the practical fat-loss effect at safe human doses is modest.

AICAR research profile.

13. BAM-15

Mitochondrial uncoupler. Animal data shows weight loss without the cardiac risk profile of older uncouplers (DNP). Human trials in progress.

BAM-15 research profile.

14. 5-Amino-1MQ

NNMT inhibitor. Preclinical data shows reduced adipose tissue accumulation. No human data yet.

5-Amino-1MQ research profile.

How to choose

A decision frame:

  • You have type 2 diabetes alongside obesity? Semaglutide or Tirzepatide. Both have T2D indications and FDA approval.
  • You have cardiovascular risk? Semaglutide has the strongest CV-outcome data (SELECT). Tirzepatide's CV outcomes trial (SURPASS-CVOT) reads 2026–2027.
  • You want the largest mean weight-loss effect from a currently-approved drug? Tirzepatide.
  • You don't tolerate Semaglutide? Tirzepatide is often better tolerated at matched-efficacy doses. Cagrilintide adds a different-mechanism option.
  • You need oral dosing (no injections)? Wait for Orforglipron approval, or use oral Semaglutide (Rybelsus) for the GLP-1 effect at lower magnitude.
  • You specifically need visceral fat reduction (HIV lipodystrophy or similar)? Tesamorelin is the on-label answer.
  • You're attached to AOD-9604 / HGH Fragment 176-191? The evidence does not support them as primary fat-loss agents at safe doses. Real expectations: minimal effect.

What about stacking?

A few practical patterns:

  • GLP-1 + amylin (Semaglutide + Cagrilintide / CagriSema) — different-mechanism complement; Phase 3 data shows additive effect.
  • GLP-1 + resistance training + protein-prioritized diet — preserves lean mass during the 20–40% lean-mass loss that otherwise accompanies rapid weight loss on GLP-1.
  • GLP-1 + Tesamorelin — used in some specialty practices to address visceral fat specifically. Evidence is weaker; the safety frame is different (GH-axis manipulation).
  • GLP-1 + healing peptides (BPC-157, TB-500) — for the joint discomfort that sometimes accompanies rapid weight loss. Not a fat-loss stack per se.

Do not stack:

  • Two GLP-1s simultaneously.
  • A GLP-1 with an old-school uncoupler (DNP) — cardiac risk is not worth the benefit.
  • A GLP-1 with stimulants in any meaningful dose — additive HR / BP effects.

What to expect

  • Onset: Appetite suppression within days of first dose.
  • Trajectory: Most weight loss in the first 6–9 months. Plateau common after.
  • Lean mass: 20–40% of weight lost is lean mass without resistance training. Disciplined training + protein cuts this meaningfully.
  • Side effects: Nausea (20–40% in trials), vomiting, diarrhea or constipation, fatigue early. Most dose-related and improve at 4–8 weeks.
  • Discontinuation: Most weight is regained within 12–24 months of stopping in the absence of behavioral change. Plan for continuation, not a "cure."

Where to go from here

This is informational, not medical advice. GLP-1-class drugs require clinician supervision in any responsible protocol. Speak to a licensed provider before starting.