Weight Loss by the Numbers
Clinical trial data tells a clear story: GLP-1 agonists dominate weight loss outcomes. Here's how the peptides compare on their primary efficacy measure — percentage of body weight lost:
Cross-trial comparison caveat: These numbers come from different trials with different populations, durations, and endpoints. Direct comparison is approximate. The only head-to-head data is SURMOUNT-5 (tirzepatide vs semaglutide), which confirmed tirzepatide's superiority.
Rankings by Evidence Strength
Tirzepatide (Mounjaro® / Zepbound®)
Tirzepatide targets both GLP-1 and GIP receptors — a dual-agonist approach that produces the highest weight loss among approved medications. The SURMOUNT-1 trial (n=2,539) demonstrated 22.5% body weight loss at the 15mg dose over 72 weeks.
In the direct comparison SURMOUNT-5 trial, tirzepatide 15mg produced 20.2% weight loss vs semaglutide 2.4mg's 13.7% — definitively demonstrating superiority.
Semaglutide (Wegovy® / Ozempic®)
The drug that launched the GLP-1 revolution. Semaglutide 2.4mg produced 14.9% weight loss in STEP 1 (n=1,961, 68 weeks). It also has cardiovascular outcome data from the SELECT trial showing a 20% reduction in MACE events — unique among weight loss drugs.
More affordable generic/compounded options and the broadest insurance coverage make it the most accessible GLP-1 agonist.
Retatrutide
The triple-agonist approach adds glucagon receptor activation (increases energy expenditure) to the dual GIP/GLP-1 mechanism. Phase 2 data (n=338) showed 24.2% weight loss at the 12mg dose over just 48 weeks — the highest ever recorded for a weight loss drug in a randomized trial.
Phase 3 trials are underway. Not yet FDA-approved as of early 2026.
Tesamorelin (Egrifta®)
Tesamorelin stimulates growth hormone release and is FDA-approved specifically for reducing visceral adipose tissue in HIV-associated lipodystrophy. It reduces visceral fat by approximately 15-18% without significant weight loss on the scale — it's a body composition drug, not a weight loss drug.
CJC-1295 / Ipamorelin
This combination stimulates natural growth hormone production, which can improve body composition over time — modestly reducing body fat while preserving lean mass. Effects are subtle compared to GLP-1 agonists: expect 2-5% body fat reduction over 3-6 months rather than dramatic weight loss.
Better suited as a body composition optimization tool, often used alongside a caloric deficit and resistance training program.
AOD-9604
AOD-9604 is a modified fragment of human growth hormone (amino acids 177-191) that was hypothesized to promote fat metabolism without GH's side effects. However, a Phase 2b trial (n=536) failed to show statistically significant weight loss versus placebo.
Approved in Australia as a food supplement ingredient. Not recommended as a primary weight loss peptide based on current evidence.
Self-Assessment
Who Researches Weight Loss Peptides?
This Research Is Commonly Explored By People Who...
- Want a comprehensive comparison of all peptides studied for weight management in one place
- Are trying to understand the differences between GLP-1, GIP, and growth hormone peptide mechanisms
- Have been overwhelmed by marketing claims and want to see what the actual clinical data shows
- Are discussing options with a healthcare provider and want to be an informed participant
- Are interested in both approved therapies and research-stage compounds for context
This Research May Not Be Relevant If...
- You're looking for a specific recommendation — this is a research comparison, not a prescription guide
- You want to self-administer peptides without medical oversight — we strongly advise against this
- You have no weight-related health concerns and are looking for cosmetic enhancements
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Key Takeaways
✅ What's Clear
- GLP-1 agonists are the gold standard for weight loss
- Tirzepatide > semaglutide in head-to-head data
- Retatrutide may be even better (Phase 3 pending)
- GH peptides help body composition, not scale weight
- All effective options require ongoing use to maintain
- Diet + exercise still matter alongside any peptide
⚠️ Important Caveats
- Cross-trial comparisons are approximate
- Individual response varies dramatically
- 25-40% of weight lost is lean mass (muscle)
- Weight regain after discontinuation is significant
- Long-term safety data still accumulating
- Cost and insurance coverage vary widely