Sydney Bueckert
Fitness Trainer
CES, FNS, GPTS, NASM-CPT
Wellness influencers, biohackers, and bodybuilders can’t seem to stop buzzing about peptides. They take them, often via injection, in hopes they’ll enhance athletic performance and optimize health.
But peptides are a wider class of substances than most people probably realize. They range from well-known FDA-approved medications like insulin and GLP-1s, to unregulated supplements like BPC-157, CJC-1295, and ipamorelin.
Meaning, some peptides are safe and effective, and others aren’t. Spoiler: If an influencer is pushing peptide supplements with a discount, it’s probably the kind you want to avoid.
Here’s what you need to know.
What Are Peptides?
Peptides are synthetic chains of amino acids that act as crucial signaling molecules in the body. They regulate important processes such as hormone balance, cell growth, immune function, and tissue repair.
Protein-rich foods (like milk, fish, and meat) naturally contain peptides, but they can also be created synthetically in a lab for supplements or drugs. Synthetic peptides are becoming increasingly popular in anti-aging skin care, and muscle growth and weight loss supplements.
Peptide therapies come with a variety of delivery methods, from subcutaneous injections to pills, nasal sprays, or topical cream. The best form depends on the specific peptide and desired effect.
Below are some of the most popular peptides for common fitness goals including weight loss, muscle growth, and body composition, and what they do (or in some cases, theoretically do) in the body:
Top Peptides for Weight Loss
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Tirezepatide: Mimics GLP-1 and GIP to manage appetite and metabolic function.
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Semaglutide: A GLP-1 agonist that slows digestion and increases satiety.
Top Peptides for Muscle Growth and Recovery
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BPC-157: Speeds up tissue healing, promoting muscle recovery and growth.
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CJC-1295: Stimulates the release of growth hormone levels, promoting muscle growth.
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TB-500: Reduces inflammation, speeding up muscle recovery.
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MK-677 (Ibutamoren): Stimulates the release of growth hormone levels, promoting muscle growth.
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IGF-1 LR3: Increases protein synthesis and reduces muscle protein breakdown.
Top Peptides for Body Recomposition
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Sermorelin: Increases growth hormone and IGF-1 levels, promoting muscle growth.
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Ipamorelin: Mimics ghrelin, a hormone that stimulates hunger, helps prevent muscle wasting, and regulates fat storage.
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Tesamorelin: Increases fat loss while maintaining muscle mass.
Does Peptide Therapy Work?
Peptide therapy shows promise for specific health goals like skin care, fat loss, and injury recovery. But its effectiveness varies widely and depends on the specific peptide used.
Certain peptides are FDA-approved for treating conditions, such as insulin for diabetes, GLP-1 agonists (like Ozempic) for weight loss, and teriparatide for osteoporosis. These medications have been proven to be effective and safe. They can be prescribed by a doctor and picked up at your local pharmacy.
However, many other peptides are experimental at best, and their benefits are unproven. Peptides like BPC-157, for example, have Reddit threads and Facebook groups full of anecdotal evidence that using them yields faster muscle recovery. But these peptides lack needed research on long-term safety and effectiveness in humans.
Are Peptides Safe?
It depends on the peptide. Generally, if your doctor is prescribing a peptide for a medical reason, and you can pick it up from a regular pharmacy you’re in the clear. This includes weight loss peptide therapies like GLP-1 agonists.
Still, these medications aren’t free of side effects. If you experience nausea, headaches, or other unwanted changes, you may be better off with a different medication, or classic lifestyle interventions like diet or exercise. Working closely with a doctor can ensure you find the best route of treatment for your needs.
Peptides that aren’t FDA-approved for human use are riskier. This includes common muscle growth and body composition peptides. BPC-157, ipamorelin, and CJC-1295 are just a few of many peptide treatments on an FDA list of substances with “significant safety concerns”.
Other popular body comp peptides like (sermorelin or tesamorelin) are approved by the FDA, but not for weight loss or muscle growth purposes. Using these peptides off-label doesn't guarantee benefits or safety.
You can still buy many non-approved peptides online, often marketed as supplements, and sold as research-grade peptides (which state on the label they’re not for pharmaceutical use). However, these products could include contaminants or unknown ingredients that could cause harm.
A doctor can also prescribe these peptides by ordering them through a compounding pharmacy, which can prepare tailored versions of drugs for individual patients, unregulated by the FDA. If you want to try off-label peptides, working with a doctor is always your safest option. But experimental peptide use is still considered a gray area, and not all doctors will prescribe them.
Compounded peptides are regulated by state boards of pharmacy and must follow USP quality standards, so they are likely safer and higher quality than supplements. However, the final compounded products aren’t reviewed for safety, effectiveness, or quality before use.
It’s also important to remember that these peptides, regardless of where you get them, are still experimental. The therapeutic dose is unknown, and you can’t just make up what dose to take.
Unwanted negative side effects are also a concern. For example, peptides that help with tissue regrowth (like IGF-1 LR3, BPC-157, or stacking CJC-1295 and ipamorelin) may also elevate insulin-like growth factor (IGF-1) levels, which could theoretically contribute to the growth of cancer cells in predisposed individuals (1). The FDA also cites increased risk of cardiac events as reasons for including CJC-1295 and MK-677 on their list of peptides with safety concerns (2).
It is wise to wait for rigorous research that a peptide works and is safe before using it.
Peptide Alternatives
Instead of relying on risky or unregulated peptides, focus on these proven, science-backed methods for body recomposition:
The Bottom Line
Peptides play an important role in medical treatments for specific conditions, and they can be a proven weight loss aid. But the jury is still out on peptide use for performance enhancement. Using peptides off-label to boost muscle gains and speed up recovery sounds good in theory but carries potentially significant risks. To optimize body composition, you’re better off focusing on evidence-based strategies like proper training, nutrition, and recovery.
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