Topic hub: fat loss
Best Peptides for Fat Loss: Ranked by Trial Effect Size
Published by Peptara Labs · Updated · How we research and check our pages
Peptides for fat loss: six compounds ranked by trial body-weight reduction. From -24.2% Phase 2 (retatrutide) to preclinical-only (SLU-PP-332). Vendor-neutral. Includes FDA status, monthly cost, and a goal-based decision tree.
Verdict in 5 lines
- Biggest trial effect: Retatrutide -24.2% body weight at 12mg/wk (Phase 2, NEJM 2023).
- Biggest FDA-approved effect: Tirzepatide -22.5% at 15mg/wk (Phase 3 SURMOUNT-1, NEJM 2022).
- Longest safety record: Semaglutide -14.9% at 2.4mg/wk (Phase 3 STEP-1, NEJM 2021). Peptara does NOT sell semaglutide.
- Visceral-fat-specific: Tesamorelin -15% VAT (not total body weight) at 2mg/day (Phase 3, NEJM 2007).
- Different trials, different cohorts, different durations. Effect-size comparison across trials is a directional observation, not a controlled head-to-head finding.
Ranked by trial effect size
Sourced from peer-reviewed clinical trials (NEJM 2007, 2021, 2022, 2023). Effect-size comparisons across separate studies are directional, not controlled head-to-head.
| Rank | Peptide | Peak Trial Effect | Phase / Source | FDA Status (obesity) | Peptara Cost |
|---|---|---|---|---|---|
| 1 | Retatrutide | -24.2% body weight | Phase 2 Jastreboff et al, NEJM 2023 | Research compound. Phase 3 ongoing. | $75 to $452 with email signup |
| 2 | Tirzepatide | -22.5% body weight | Phase 3 Jastreboff et al, NEJM 2022 (SURMOUNT-1) | Zepbound FDA-approved Nov 2023 (brand pen). Peptara sells research vial; single vials currently sold out, available in the Lumen research stack. | $42 to $253 with email signup |
| 3 | Semaglutide (Ozempic / Wegovy) | -14.9% body weight | Phase 3 Wilding et al, NEJM 2021 (STEP-1) | Wegovy FDA-approved Jun 2021 | NOT sold by Peptara. US retail $968 to $1,349/mo |
| 4 | Tesamorelin | -15% visceral adipose tissue (VAT) | Phase 3 Falutz et al, NEJM 2007 | FDA-approved 2010 (HIV-associated lipodystrophy). Off-label / research for general VAT. | about $440/mo with email signup (1mg/day) |
| 5 | MOTS-c | Metabolism + insulin sensitivity (no Phase 3 obesity trial) | Preclinical + small human Lee et al, Cell Metab 2015 | Research compound | $85 to $170/mo with email signup (5 to 10mg/wk) |
| 6 | SLU-PP-332 | Exercise mimetic (no human obesity trials) | Preclinical (mouse only) Billon et al, J Pharmacol Exp Ther 2023 | Research compound | $157/vial with email signup, biohacker dosing varies |
Read this before quoting the ranking
Different trials, different cohorts, different durations, different placebo response calibration. These effect sizes are a directional comparison across separate studies, not a controlled head-to-head finding. Retatrutide Phase 3 results from the TRIUMPH program may report different numbers than Phase 2. SURMOUNT-1 ran 72 weeks; STEP-1 ran 68 weeks. Tesamorelin measured visceral fat (VAT) not total body weight, which is a different endpoint.
Decide by goal
Six goal profiles, six recommendations. Pick the card that matches what you actually care about.
Goal A
Biggest weight loss number
Triple-agonist GLP-1 + GIP + glucagon. Largest trial effect (-24.2% Phase 2). Trade-off: Phase 3 still collecting. Research compound, not FDA-approved.
Pick: Retatrutide
Goal B
FDA-approved, longest safety record
Single-agonist GLP-1. Years of cardiovascular outcome data (SUSTAIN, SELECT). Trade-off: smallest trial effect of the GLP-1 class (-14.9% STEP-1). US retail $968 to $1,349/mo cash. Peptara does NOT sell semaglutide.
Pick: Semaglutide (Ozempic / Wegovy)
Goal C
FDA-approved, biggest trial effect
Dual-agonist GLP-1 + GIP. -22.5% Phase 3 SURMOUNT-1. FDA-approved as Mounjaro (T2D, 2022) and Zepbound (obesity, 2023). Peptara sells research vial at 10 to 15x lower starting-dose cost.
Pick: Tirzepatide
Goal D
Belly / visceral fat specifically
GHRH analog. Stimulates pulsatile GH leading to IGF-1 leading to preferential VAT reduction. Different endpoint: -15% visceral adipose tissue (NOT total body weight). FDA-approved 2010 (Egrifta) for HIV-associated lipodystrophy. Used off-label or research for visceral fat in non-HIV populations.
Pick: Tesamorelin
Available via Peptara, no dedicated product page yet. Contact WhatsApp.
Goal E
Metabolism + insulin sensitivity, no GLP-1 GI
Mitochondrial-derived peptide. Boosts cellular energy and insulin sensitivity. Fat-loss-adjacent, not primary fat-loss. No Phase 3 obesity trial. Preclinical plus small human studies on aging and metabolism.
Pick: MOTS-c
Available via Peptara, no dedicated product page yet. Contact WhatsApp.
Goal F
Endurance / fat oxidation, not appetite suppression
ERR receptor agonist. Exercise-in-a-vial mechanism. Preclinical mouse data only. NO human obesity trials. For research / biohacker use, not validated for fat loss in humans.
Pick: SLU-PP-332
Available via Peptara, no dedicated product page yet. Contact WhatsApp.
Mechanism groups
Three biological pathways, six compounds.
GLP-1 class (appetite + metabolic)
Retatrutide (triple agonist), Tirzepatide (dual), Semaglutide (single). Activate the gut-brain satiety axis plus insulin / glucagon regulation. Mechanism of action shared; receptor count differs.
GH axis (visceral fat-specific)
Tesamorelin (GHRH analog). Stimulates endogenous GH release leading to IGF-1 leading to preferential visceral adipose tissue reduction. Different endpoint than GLP-1s.
Mitochondrial / exercise mimetic
MOTS-c (mitochondrial peptide), SLU-PP-332 (ERR agonist). Boost cellular energy and fat oxidation. Less validated for fat loss; closer to metabolic optimization. Emerging class.
Cost breakdown
Peptara monthly cost ranges with the email-signup rate applied. Cost formula: vial price times 4.33 weeks per month, divided by weeks per vial.
| Peptide | Vial | Email signup / Retail | Common Dose | Monthly email rate | Monthly retail |
|---|---|---|---|---|---|
| Retatrutide | 20mg | $174 / $205 | 2mg to 12mg/wk titration | $75 to $452 | $89 to $533 |
| Tirzepatide | 20mg | $78 / $92 | 2.5mg to 15mg/wk titration | $42 to $253 | $50 to $299 |
| Tesamorelin | 10mg | $144 / $170 | 1mg/day common research | about $440 | about $515 |
| MOTS-c | 40mg | $157 / $185 | 5 to 10mg/wk | about $85 to $170 | about $100 to $200 |
| SLU-PP-332 | 5mg | $157 / $185 | Research-only, varies | Varies | Varies |
External US retail reference (not Peptara pricing)
Ozempic about $968/mo, Wegovy about $1,349/mo (Novo Nordisk cash list). Compounded semaglutide about $200 to $400/mo (FDA-restricted after October 2024 shortage resolution). Peptara does NOT sell semaglutide.
Monthly cost calculation: vial price times 4.33 weeks/month divided by weeks per vial. Reta and Tirz use 20mg per vial reconstituted in 2mL bac water for 200 units per vial at 0.1mg per unit. Doses always in units, never mL. See the reconstitution guide for full math.
Stacking framework
What to combine, what to avoid, how to sequence.
Smart stacks
- Retatrutide OR Tirzepatide plus Tesamorelin (total body + visceral)
- Retatrutide OR Tirzepatide plus MOTS-c (appetite + insulin sensitivity)
- GLP-1 plus CJC-1295 / Ipamorelin (lean mass retention during fat loss). See the research stacks.
Avoid
- Retatrutide + Tirzepatide (redundant GLP-1 mechanism, additive GI)
- Tirzepatide + Semaglutide (redundant GLP-1, GI compounding)
- Retatrutide + Semaglutide (redundant; sema is FDA-approved Rx, do not mix with research compound without physician guidance)
Sequencing
- Stopping a GLP-1 is followed by appetite and glucose homeostasis adjustment, a question for the prescribing clinician
FDA status and regulatory landscape
Two FDA-approved as brand pens (Tirz, Sema). One FDA-approved for a specific non-obesity indication (Tesamorelin, HIV-associated lipodystrophy). Three research compounds.
| Peptide | Status | FDA Approval Date | Available Form |
|---|---|---|---|
| Retatrutide | Research compound | Phase 3 ongoing (TRIUMPH program) | Research vial only |
| Tirzepatide | FDA-approved (brand pens) | Mounjaro May 2022 (T2D), Zepbound Nov 2023 (obesity) | Brand pre-filled pen via Rx; research vial via Peptara |
| Semaglutide (Ozempic / Wegovy) | FDA-approved (brand pens) | Ozempic Dec 2017, Wegovy Jun 2021 | Brand pre-filled pen via Rx ONLY. Peptara does not sell. |
| Tesamorelin | FDA-approved (Egrifta) | Nov 2010 | FDA-approved for HIV-associated lipodystrophy. Off-label / research for general VAT reduction. |
| MOTS-c | Research compound | N/A | Research vial only |
| SLU-PP-332 | Research compound | N/A | Research vial only (preclinical data; not for clinical use) |
Side effects by mechanism group
Three profiles to know.
GLP-1 class (Reta + Tirz + Sema)
Nausea, diarrhea, constipation, vomiting. Most pronounced during titration and at higher doses; usually resolves over 4 to 8 weeks per dose step. GLP-1 class carries thyroid C-cell black-box warning (rodent signal; no confirmed human cases). Trial-reported nausea rates: retatrutide about 30% at 12mg (Jastreboff et al., NEJM 2023), tirzepatide about 30% at 15mg (SURMOUNT-1, Jastreboff et al., NEJM 2022), semaglutide about 20% at 2.4mg (STEP-1, Wilding et al., NEJM 2021).
GH-axis (Tesamorelin)
Injection-site reactions, joint pain, fluid retention. May elevate IGF-1 (monitor lab values for longer protocols). Avoid in active malignancy and diabetic retinopathy.
Mitochondrial + exercise mimetic (MOTS-c, SLU-PP-332)
Limited human data. MOTS-c well-tolerated in small studies. SLU-PP-332 long-term human safety not established (preclinical only). Standard research-compound caveats apply.
Timeline expectations
How long until you see effects.
| Peptide | Dose Schedule | Time to Visible Effect |
|---|---|---|
| Retatrutide | Weekly injection | 4 to 8 weeks at starting dose; major weight change at 24+ weeks |
| Tirzepatide | Weekly injection | 4 to 8 weeks at starting dose; major weight change at 24+ weeks |
| Semaglutide | Weekly injection (brand pen) | 4 to 8 weeks at starting dose; major weight change at 24+ weeks |
| Tesamorelin | Daily injection | 12 to 26 weeks for visceral fat measurable reduction |
| MOTS-c | 2x weekly | 4 to 12 weeks for insulin sensitivity and metabolic markers |
| SLU-PP-332 | Research-protocol-dependent | No human obesity timeline established |
Frequently asked questions
Which peptide loses the most weight?
Retatrutide showed the largest mean body-weight reduction in trials at -24.2% over 48 weeks (Jastreboff et al, Phase 2, NEJM 2023). Tirzepatide is the largest FDA-approved effect at -22.5% over 72 weeks (Jastreboff et al, Phase 3 SURMOUNT-1, NEJM 2022). Semaglutide (Ozempic / Wegovy) is -14.9% (Wilding et al, Phase 3 STEP-1, NEJM 2021). These are separate trials with different cohorts and different durations, so the comparison is a directional observation, not a controlled head-to-head finding.
Are GLP-1 peptides the only option for fat loss?
No. Tesamorelin (GHRH analog) is FDA-approved (2010) and targets visceral adipose tissue specifically, not total body weight. MOTS-c (mitochondrial peptide) and SLU-PP-332 (ERR agonist exercise mimetic) operate via different metabolic pathways. GLP-1 agonists (Reta, Tirz, Sema) currently produce the largest measured fat-loss effects, but they are not the only peptides studied for body-composition outcomes.
Can I stack Retatrutide with Tirzepatide?
No. Both are GLP-1 agonists with overlapping mechanism. Stacking them is redundant and adds GI side-effect burden without additional fat-loss benefit.
Does Peptara sell Ozempic or Wegovy?
No. Peptara does NOT sell semaglutide in any form. Peptara is a research-peptide supplier. Brand pens (Ozempic, Wegovy, Mounjaro, Zepbound) are FDA-approved finished pharmaceuticals available only via prescription. Anyone selling brand pens online is selling gray-market product with no chain-of-custody guarantee. Peptara stocks Retatrutide, Tirzepatide, Tesamorelin, MOTS-c, and SLU-PP-332 as research vials. Tirzepatide single vials are currently sold out and available in the Lumen research stack.
What is the difference between visceral and subcutaneous fat loss?
Subcutaneous fat is the layer under the skin (what you can pinch). Visceral fat (VAT) is the deep abdominal fat surrounding internal organs; it is metabolically distinct and more strongly tied to insulin resistance, cardiovascular risk, and type 2 diabetes. GLP-1 agonists (Reta, Tirz, Sema) reduce both compartments via total body weight loss. Tesamorelin specifically targets VAT (-15% in Phase 3) without comparable subcutaneous effect.
Are there fat-loss peptides without GLP-1 side effects (nausea, etc.)?
Yes. Tesamorelin (GH axis), MOTS-c (mitochondrial), and SLU-PP-332 (ERR agonist) operate outside the GLP-1 pathway and do not share the appetite-mediated GI profile. Trade-off: smaller effect on total body weight than the GLP-1 class, and less clinical validation. Tesamorelin is the most validated non-GLP-1 option for fat-targeting (FDA-approved 2010 for VAT reduction).
How long until I see results?
GLP-1 class (Reta, Tirz, Sema): 4 to 8 weeks at starting dose for early appetite and scale changes; major body weight reduction typically takes 24+ weeks of titration to peak dose. Tesamorelin: 12 to 26 weeks for visceral fat measurable reduction (imaging-based endpoint). MOTS-c: 4 to 12 weeks for insulin sensitivity / metabolic marker changes. Individual response varies substantially.
Is FDA approval important if the molecule is the same?
FDA approval certifies the finished pharmaceutical (manufacturing, fill-finish, sterility, labeling, dose accuracy), not the molecule itself. The molecule is identical whether it is Mounjaro brand pen or a research vial of tirzepatide. What differs is the regulatory pathway (Rx-only finished product vs research compound), the supply chain (pharmacy chain-of-custody vs research supplier), the packaging (pre-titrated pen vs lyo vial requiring reconstitution), and the price (FDA-approved finished product carries the FDA-approval premium). Choose based on regulatory comfort, format preference, and budget.
Next steps
Retatrutide product page
Triple-agonist research vial. $174 with email signup / $205 retail. 20mg/vial.
View product
Tirzepatide product page
Dual-agonist research vial (same molecule as Mounjaro / Zepbound). $78 with email signup / $92 retail. 20mg/vial.
View product
How to reconstitute your vial
4-step method plus units-not-mL calculator. Required reading before any research-vial protocol.
Open guide
Full /vs/* cluster
Questions about these compounds
Message the Peptara team on WhatsApp and we will point you at what the research describes for each fat-loss compound.
We answer protocol questions, not medical questions. For Tesamorelin, MOTS-c, and SLU-PP-332 (no dedicated product page yet), WhatsApp is the order channel.
Keep reading
GLP-1 research guides and comparisons
Semaglutide dosage
What the STEP trials used, in units not mL.
Semaglutide side effects
Reported effects from the trial record.
Semaglutide results timeline
What the trials measured over time.
Semaglutide half-life
Why it is a once-weekly compound.
Cagrilintide
The amylin analog studied alongside GLP-1s.
Survodutide
The GLP-1 and glucagon dual agonist.
AOD-9604
The fragment marketed for fat loss.
Tirzepatide vs Semaglutide vs Retatrutide
The three headline GLP-1 compounds, compared.
Cagrilintide vs Semaglutide
Amylin plus GLP-1 vs GLP-1 alone.
Survodutide vs Retatrutide
Two multi-agonists, compared.
AOD-9604 vs Semaglutide
Fragment vs GLP-1, by the evidence.
Tesamorelin vs Semaglutide
GH-axis visceral fat vs GLP-1 weight loss.