Peptides have become one of the hottest subjects in the modern fitness and longevity world, promising everything from faster recovery and more muscle to less body fat, better sleep, and fewer aches. But Jordan D. Metzl, MD, a sports medicine physician at New York’s Hospital for Special Surgery, says the growing enthusiasm needs to be separated from what medicine actually knows.
In a September 28 Washington Post column, Metzl described a patient who asked whether he should take peptides to feel better, recover faster, and remain healthy as he aged. The question is on par with a broader trend fueled by friends, podcasts, and social media.
Not Every Peptide Is Experimental
The word “peptide” can sound like a single category of treatment, but Metzl stresses that these compounds vary dramatically. Peptides are short chains of amino acids, and some have decades of human research behind them. Insulin, for example, is a peptide-based medication.
Semaglutide provides another important distinction. The GLP-1 receptor agonist has been tested in large randomized clinical trials, unlike many compounds being promoted through wellness clinics and online sellers.
A 2024 New England Journal of Medicine involving people with obesity and painful knee osteoarthritis found that participants taking semaglutide for 68 weeks lost an average of 13.7 percent of their body weight, compared with 3.2 percent among those receiving placebo. They also experienced substantially less knee pain and improved physical function.
For a sports medicine physician, Metzl says the significance extends beyond weight loss. Reduced weight can mean less joint pain, making movement easier for people who otherwise struggle to exercise.
The Bigger Peptide Craze Has a Different Evidence Problem
That evidence should not be confused with the research behind compounds such as BPC-157, TB-500, CJC-1295, and ipamorelin. These substances are marketed for tendon healing, recovery, inflammation, muscle growth, aging, fat loss, and athletic performance, yet Metzl says their scientific foundation is nowhere near as strong as semaglutide’s.
For some popular recovery peptides, the available evidence consists largely of animal research, laboratory experiments, or very small human studies. That leaves major unanswered questions about effectiveness, appropriate dosing, which patients might benefit and, most importantly, long-term consequences.
The Food and Drug Administration has raised concerns about limited safety information surrounding many of these compounds because human exposure data remain scarce. Meanwhile, the regulatory conversation has included proposals concerning whether certain experimental peptides could be prepared by compounding pharmacies. Proponents believe physician-supervised access could be safer than the poorly regulated “gray market.”
But compounding is not equivalent to FDA approval. It does not establish that a substance heals tendons, speeds recovery, or extends lifespan, nor does it provide the same evidence of safety and effectiveness or the same manufacturing oversight associated with approved medications.
Metzl’s Message: Evidence Before Excitement
martin-dm / Getty Images
Metzl’s central concern is the gap between biological possibility and medical proof. A compound producing an effect in a laboratory, showing promise in an animal or accumulating glowing online testimonials does not establish what happens after five or 10 years of human use.
That does not mean peptides should be abandoned. Metzl argues that they deserve more research, particularly because they could eventually offer new approaches to obesity, muscle preservation, pain reduction, and healthy aging.
For now, though, his advice is deliberately less glamorous: exercise, strength training, good sleep, and healthy eating remain foundational. Patients considering experimental peptides should understand that the science and manufacturing standards may not match those of approved medicines.
The peptide era could prove transformative. But , medicine does not yet know where all of these compounds will lead. The crucial distinction is between what looks promising and what has actually been demonstrated in people.