The promise and perils of the peptide craze

The peptide revolution is real. But every molecule must be judged by the quality of evidence behind it, not by the enthusiasm surrounding it

A few days ago, a 45-year-old woman came to me seeking treatment for obesity. She was not diabetic, but was about 20 kilos overweight and could be a suitable candidate for medication. I began explaining tirzepatide (Mounjaro), including its benefits and potential side effects. She cut me short. “I don’t want Mounjaro. I’ve heard a lot about its side effects.”

A peptide is a chain of amino acids, the building blocks of proteins. Our bodies naturally produce hundreds of peptides. Important hormones, including insulin, glucagon, oxytocin, and vasopressin, belong to this family. (Shutterstock)

I asked what she would prefer instead.

“Retatrutide. All my friends are taking it.”

I asked whether she understood its potential risks and knew that it had not yet been approved for routine clinical use. She replied that she had learnt enough about it from Instagram and Reddit. Here was someone worried about the side effects of an established medicine, yet requesting a drug still under clinical development. This, in many ways, typifies the current peptide craze. The word peptide has acquired an almost magical quality. Peptides are discussed everywhere, from obesity clinics and gyms to social media and longevity centres. They are promoted for weight loss, muscle building, better skin, faster recovery, anti-ageing, and even longevity. Some of you might have read about the peptide party that was planned in Bangalore last month but had to be cancelled due to intervention by the authorities.

What exactly is a peptide? A peptide is a chain of amino acids, the building blocks of proteins. Our bodies naturally produce hundreds of peptides. Important hormones, including insulin, glucagon, oxytocin, and vasopressin, belong to this family. Insulin has been used for more than a century. Three developments explain the current enthusiasm. First, advances in biotechnology allow scientists to design and modify peptides with remarkable precision, improving their stability and actions. Second, the success of GLP-1-based medicines has transformed obesity and diabetes treatment. Semaglutide and tirzepatide demonstrate how manipulating hormonal pathways regulating appetite, satiety and metabolism can produce substantial weight loss. Third, social media and the wellness industry have extended the word peptide far beyond evidence-based medicine. Products are promoted for muscle growth, tissue repair, skin rejuvenation, and longevity, often with claims that far exceed the available evidence.

Retatrutide takes the GLP1 approach a step further, activating three receptors: GIP, GLP-1 and glucagon. Clinical trials have reported impressive weight-loss results, generating considerable excitement about its potential. It may eventually become an important addition to obesity treatment. But promising trial results are not the same as established long-term safety. And neither of the two is equivalent to regulatory approval. Further evaluation must establish its benefits and risks use.

Drug development is littered with molecules that showed promise in early studies but never became successful medicines. The journey from laboratory discovery to an approved drug requires toxicology studies, carefully conducted clinical trials, assessment of benefits and risks, manufacturing quality standards, and regulatory scrutiny. This process is an essential safeguard. Buying an unapproved product online and injecting it bypasses these protections.

Alongside legitimate medicines, an expanding market has emerged for compounds such as BPC-157, TB-500, CJC-1295, ipamorelin, AOD-9604, GHK-Cu, MOTS-c and epithalon. Open the mini-fridge of a 26-year-old fitness trainer in Vasant Kunj or a startup founder in Gurugram, and you might find, next to the eggs, a rack of small vials labelled BPC-157, TB-500 or CJC-1295 with ipamorelin. The labels sound scientific, and the claims are even more enticing. BPC-157 has shown interesting effects in animal studies on tissue repair. TB-500 is marketed for healing and recovery. CJC-1295 and ipamorelin are promoted for stimulating growth hormone release. MOTS-c is sold for metabolic benefits, while epithalon is marketed with claims relating to sleep and ageing. But biological plausibility is not proof of clinical benefit. Findings in cells or animals do not establish that a compound is effective or safe in humans. Most of these products lack the robust clinical evidence needed to support their marketing claims and are not approved medicines for wellness, recovery or longevity. Poor product quality and lack of dosing standardisation can result in reactions including local infections, even sepsis. A vial labelled “pure peptide” does not guarantee safety.

An influencer displays an MRI scan showing dramatic improvement after taking a peptide. What we do not see are the people who experienced no benefit, those who developed complications, or the possibility that the improvement had another explanation. Personal anecdotes can generate hypotheses; they cannot establish efficacy.

My patient’s response illustrates a larger problem. Concerns about adverse effects deserve to be taken seriously and discussed openly. But there is a fundamental difference between rejecting a medicine because its risks are known and assuming that an inadequately studied alternative must be safer. With an established medicine, we generally have a much clearer understanding of its benefits, adverse effects, contraindications and precautions. With an investigational compound, important risks may simply remain undiscovered. The absence of known adverse effects is not evidence of safety. Sometimes, it merely reflects an absence of adequate study. Retatrutide is an exciting development in metabolic medicine. It deserves rigorous evaluation, not premature adoption. The same principle applies to the wider peptide market.

Insulin transformed diabetes from a once-fatal disease into a manageable condition. Modern incretin-based therapies are transforming obesity and type 2 diabetes treatment. The peptide revolution is real. But every molecule must be judged by the quality of evidence behind it, not by the enthusiasm surrounding it.

You are not a laboratory rat. A compound that produces an interesting effect in an animal is not necessarily suitable for human use. Nor should you become an unwitting participant in an uncontrolled experiment because a friend, fitness coach or social media influencer recommends an injectable product. Ask yourself: why does this supposed miracle treatment have to be bought from an online stranger, kept in a fridge next to your eggs, and injected on the advice of a reel?

The future of peptide medicine is exciting. But genuine progress depends on separating scientific promise from commercial hype. Before injecting a peptide, ask your doctor. Your health deserves evidence, not experiments.

Ambrish Mithal is chairman and head of Endocrinology and Diabetes at Max Healthcare. The views expressed are personal