Peptides for Weight Loss: GLP-1, Tesamorelin, and What Actually Works

Peptides for Weight Loss: Ranked by Evidence

GLP-1 Peptides: The Clear Leaders

Semaglutide (Ozempic for diabetes, Wegovy for obesity) and tirzepatide (Mounjaro for diabetes, Zepbound for obesity) are GLP-1 receptor agonists — peptide-based drugs that produce weight loss primarily through appetite suppression and slowed gastric emptying. The STEP 1 trial showed average weight loss of 14.9% of body weight over 68 weeks on semaglutide 2.4 mg. The SURMOUNT-1 trial showed 22.5% average weight loss on tirzepatide 15 mg.

Retatrutide — a triple agonist targeting GIP, GLP-1, and glucagon receptors — showed 24.2% average weight loss at 48 weeks in Phase II data. Phase III trials are ongoing. If results hold, it may become the most effective weight-loss drug ever approved.

These are the only peptides where the evidence clearly supports expecting significant (>10%) body weight reduction in the majority of patients.

Growth Hormone Peptides: Body Composition vs. Weight Loss

Growth hormone secretagogues (ipamorelin, sermorelin, CJC-1295, tesamorelin) are often marketed for weight loss, but their primary effect is on body composition — not scale weight. They work by stimulating your pituitary to release more growth hormone, which:

• Reduces visceral fat: GH selectively mobilizes visceral adipose tissue. Tesamorelin specifically reduced visceral fat by 15–20% in FDA trials.
• Increases lean muscle mass: GH is anabolic. Users often simultaneously lose fat while gaining muscle — meaning the scale may not move much even as body composition improves significantly.
• Improves sleep quality: GH is predominantly released during slow-wave sleep. Better GH pulses improve sleep architecture, which in turn supports fat metabolism.

If your goal is specifically to see the scale move, GH peptides will likely disappoint. If your goal is to reduce abdominal fat and improve body composition — while maintaining or building muscle — they can be genuinely effective. The combination of ipamorelin + CJC-1295 is the most commonly used GH stack for body recomposition.

Tesamorelin for Visceral Fat

Tesamorelin is the standout peptide for targeted visceral fat reduction. FDA-approved for HIV-associated lipodystrophy (abnormal abdominal fat), its mechanism is relevant to anyone with excess visceral fat — a common feature of metabolic syndrome, insulin resistance, and post-menopausal fat redistribution.

Clinical data shows 15–20% reduction in visceral adipose tissue over 26 weeks. Unlike GLP-1 agonists, tesamorelin doesn't strongly suppress appetite — it works through a different mechanism entirely (GH stimulation → IGF-1 → lipolysis). This makes it useful for people who want to target abdominal fat without the GI side effects of GLP-1 drugs.

Access outside of HIV lipodystrophy requires working with a provider who prescribes it off-label — it remains available through compounding pharmacies for body composition purposes.

Peptides That Don't Work for Weight Loss

Several peptides are frequently marketed for weight loss without supporting evidence:

• AOD-9604: A GH fragment marketed heavily in the supplement space. Failed Phase III trials for obesity. Does not produce meaningful weight loss in humans at tolerable doses.
• HCG (human chorionic gonadotropin): The FDA has explicitly stated the HCG diet is "dangerous and illegal." The weight loss seen on HCG protocols is from the accompanying 500-calorie diet, not the hormone. HCG does not cause fat mobilization as claimed.
• MK-677 (ibutamoren): A non-peptide GH secretagogue. While it raises IGF-1 and GH, it does NOT cause weight loss — it significantly increases appetite. Many users gain weight due to water retention and increased food intake.