{"id":32004,"date":"2026-05-16T06:00:40","date_gmt":"2026-05-16T04:00:40","guid":{"rendered":"https:\/\/cristinatomasi.com\/?p=32004"},"modified":"2026-05-22T14:37:18","modified_gmt":"2026-05-22T12:37:18","slug":"peptides-between-biological-promise-and-marketing","status":"publish","type":"post","link":"https:\/\/cristinatomasi.com\/en\/peptidi-tra-promessa-biologica-e-marketing\/","title":{"rendered":"Peptides: Between Biological Promise and Marketing"},"content":{"rendered":"

What are peptides really, and why is most of what you hear about them inaccurate?<\/strong><\/h2>\n

In the last two years, peptides they have become the hot topic in wellness medicine<\/strong>. You can find them in podcasts by longevity<\/strong>, in the reels of biohacking<\/strong>, in the protocols of famous athletes. They promise to burn fat<\/strong> without moving, repair tendons<\/strong> in two weeks, sleep<\/strong> like a child, slow down aging<\/strong>. And the public, understandably, is confused: are they a revolution or just another fad?<\/p>\n

The most honest answer<\/strong>, which you rarely find in marketing, is:\u00a0neither one nor the other<\/strong>. Peptides are a real and interesting biological class, with enormous theoretical potential. But there is a gap between theoretical potential and \u201cit works today, on you\u201d that marketing pretends not to see.<\/p>\n

This week we are focusing precisely on that distance.<\/p>\n

 <\/p>\n

Technically, peptides are short chains of amino acids linked together by peptide bonds.<\/strong><\/h3>\n

 <\/p>\n

One peptide<\/strong> is a amino acid chain<\/strong> held together by chemical bonds called, precisely, peptide bonds. When the chain is short, conventionally up to 50 or 100 amino acids, we call it a peptide. When it's longer, we call it a protein<\/strong>. The difference is a convention, not a chemical revolution: from a molecular point of view, Peptides and proteins belong to the same family<\/strong>.<\/p>\n

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Like this pearl necklace: Each pearl represents an amino acid<\/strong>. If the chain contains up to 100 beads, it is called a peptide; if the chain is made up of more than 100 beads, it is called a protein. There is a peptide bond between each bead.<\/p>\n

This is the first important point to clarify<\/strong>, because it helps dismantle the idea that peptides are something exotic. They are not. Your body produces them all the time.<\/p>\n

The\u2019insulin<\/strong>, which regulates blood sugar, is a peptide. The\u00a0glucagon<\/strong>, which does the opposite, is a peptide. The\u2019oxytocin<\/strong>\u00a0is a peptide involved in affective bonding and childbirth.\u00a0Endorphins<\/strong>\u00a0Peptides are what give you a sense of well-being after a run.\u00a0leptin<\/strong>, who tells you to stop eating, and the\u00a0ghrelin<\/strong>, which tells you to do it, are peptides. Even the\u00a0GLP-1<\/strong>, the molecule behind Ozempic and Mounjaro that has revolutionized weight loss, is a peptide.<\/p>\n

An important clarification: all of these are peptide hormones. Structurally, they are peptides in every respect, but functionally, they behave like hormones: that is, molecules that produce a direct effect on the body, regardless of what is<\/h3>\n

This happens in all situations. Insulin lowers blood sugar even if you were fasting. Oxytocin has precise effects even if you are not in love. Pharmacological GLP-1 reduces appetite even if you didn't have a \u201csatiety signal\u201d to amplify.<\/p>\n

 <\/p>\n

Keep this distinction in mind<\/strong>, Because below we will see that most of the wellness marketing peptides work very differently. They are structurally peptides, but they are not hormones: they do not produce a direct effect. They work in another mode, and that is the source of much of the confusion.<\/p>\n

So when you hear someone say,\u201cPeptides are the future of medicine<\/strong><\/em>\u201c the phrase is true in a trivial sense: I already am, and have been for decades<\/strong>, in the form of life-saving approved medications every day. The problem is that marketing uses the same word, \u201cpeptides,\u201d to refer to very, very different things.<\/p>\n

 <\/p>\n

The real point: peptides amplify a signal, they don't create it<\/strong><\/h3>\n

Let's pick up where we left off. We've seen that many endogenous peptides (insulin, GLP-1, oxytocin) are actually hormones and produce a direct effect. Most peptides that you find sold as \u201ctonics,\u201d \u201canti-aging\u201d agents, or \u201cfat-burners\u201d work differently. This is probably the most important idea in this entire newsletter, so I'll take a moment to explain it thoroughly.<\/p>\n

Drugs that have a direct effect on the body work predictably: you take the molecule, the molecule does its thing, and you feel the result.\u00a0amphetamine<\/strong>\u00a0they still stimulate you, even if you were previously unwilling or relaxed. The\u00a0T3<\/strong>\u00a0it speeds up your metabolism anyway, even if your thyroid was working well. The\u00a0Exogenous testosterone<\/strong>\u00a0It boosts testosterone anyway, even if your body was producing enough.<\/p>\n

Most peptides advertised today\u00a0That's not how it works.<\/strong>. They don't create an effect from scratch. They simply amplify a signal that your body is already emitting.<\/p>\n

If you train, your body sends a signal for muscle growth, and a peptide can amplify this signal. If you are in a caloric deficit, your body already has a signal to lose weight, and a peptide like tesamorelina can amplify it and accelerate the process. If you are injured, healing processes are already active, and a regenerative peptide can speed them up. If you sleep, sleep phases are already present, and some molecules can make them deeper.<\/p>\n

But if there's no baseline signal, there's nothing to amplify.<\/strong>\u00a0Injecting yourself with a peptide thinking you'll lose weight without changing your diet, or gain muscle without going to the gym, It's like turning up the volume on a radio that's off.<\/strong> Peptide marketing sells exactly this illusion, and it's the main reason why most people are disappointed: they spend a ton of money expecting miracles, and in many cases, they feel nothing.<\/p>\n

Stated positively: many peptides\u00a0they reward those who are already working<\/strong>. If you train consistently, eat sensibly, and respect your circadian rhythm, then a well-chosen peptide can make weight loss a little faster and easier, recovery a little more complete, and adaptation a little more effective. It's an extra gear for an already running machine. But if the machine is stopped, no gear will help.<\/p>\n

 <\/p>\n

A concrete example: tesamorelina versus exogenous GH<\/strong><\/h3>\n

To truly understand the difference between \u201camplify\u201d and \u201cdirectly inject,\u201d let's take a real-world case: the\u00a0Tesamorelin<\/strong>.<\/p>\n

Tesamorelin is one of the few FDA-approved peptides, indicated for lipodystrophy (increased visceral fat) associated with HIV. It is a GHRH analog, meaning it mimics the hormone that your hypothalamus produces to tell the pituitary gland to release growth hormone (GH), our body's most potent lipolytic (or \u201cfat-burning\u201d) agent. When you inject it, tesamorelin binds to pituitary gland receptors and stimulates a larger pulse of GH than you would have naturally.<\/p>\n

Crucial point: this pulsation remains within the physiological range. Your body continues to regulate itself normally. Insulin, for example, is an antagonist of GH: if you eat carbohydrates 5 minutes after the injection, insulin rises, GH drops, and the effect is attenuated: in other words, you have spent money and injected a molecule for nothing.<\/p>\n

If you instead inject\u00a0Exogenous GH<\/strong>, ..., the actual hormone, you completely bypass this mechanism. You reach supra-physiological levels, independent of the body's negative feedback: no matter how many carbohydrates you eat or what else you do, you will still have high GH levels. The effect is more powerful, more direct, more predictable, but also much riskier, and far beyond what your organism had ever \u201cpredicted.\u201d.<\/p>\n

This is the difference between amplifying a signal and injecting it directly. It's why peptides are never a shortcut to skipping lifestyle changes: they are, at best, an amplifier of something you're already doing.<\/p>\n

 <\/p>\n

The theoretical potential is truly enormous<\/strong><\/h3>\n

I want to be honest here and balance the discussion, because there's a risk of coming across as a total skeptic. I'm not. On paper, some of these peptides are among the most fascinating things molecular biology has ever studied.<\/p>\n

Think about\u00a0MOTS-c<\/strong>: It is a peptide encoded not by nuclear DNA, but by mitochondrial DNA. It is endogenous\u2014your body produces it\u2014and acts as a bridge between the cells\u201c energy powerhouses and systemic metabolism. It mimics some of the effects of physical exercise by activating the same biochemical pathways involved in fat metabolism and AMPK; this is why it is also marketed as \u201dexercise in a bottle.\u201d And in animal models, higher levels of MOTS-c appear to correlate with greater longevity. Studies in humans have shown that plasma levels of MOTS-c decline by 10\u201320% with aging. A molecule that restores a biological parameter that declines with age\u2014the idea is fascinating.<\/p>\n

Think about the\u2019Epitalon<\/strong>a small tetrapeptide that, in the studies of the Russian group of Khavinson, induces the expression of hTERT, the enzyme that reconstructs telomeres. In simple terms: telomeres are the \u201cprotective caps\u201d at the ends of our chromosomes, which shorten with each cell division and function as a sort of biological clock. When they are completely used up, the cell stops dividing and undergoes death, and this progressive shortening is considered one of the mechanisms underlying aging. Lengthening them, at least theoretically, would mean rewinding part of that clock., meaning to extend life and slow down aging<\/strong>.<\/p>\n

Think about\u00a0GHK-Cu, the peptide of youth and beauty<\/strong>: a copper-bound tripeptide, naturally present in our body, whose plasma levels decrease with age. Its most studied and established application is on the skin: it stimulates the production of\u00a0collagen and elastin<\/strong>\u00a0(the two structural proteins that give tone, support, and elasticity) promotes fibroblast regeneration, accelerates wound healing, and shows antioxidant and anti-inflammatory effects. For this reason, it has been found for decades in high-end dermocosmetic serums and creams. But its most intriguing aspect is another: studies from the Broad Institute have shown that it modulates the expression of\u00a0over 4000 human genes<\/strong>a statistic that marketing loves to cite as proof that it \u201ctakes you back to youth.\u201d (Spoiler: \u201cmodulate\u201d doesn't mean \u201cactivate toward youth,\u201d but the statistic is real and fascinating.)<\/p>\n

All of this is extraordinary on paper. The problem is that \u201con paper\u201d and \u201cin practice, today, on a human being\u201d are two very different places.<\/p>\n

 <\/p>\n

The current state of evidence, today<\/strong><\/h3>\n

Where marketing almost always stumbles is here: the\u00a0The available scientific literature is almost entirely preclinical.<\/strong>.<\/p>\n

Specifically, it means that most of what we know comes from:<\/p>\n

    \n
  • Cell culture studies in the laboratory (in vitro);<\/li>\n
  • studies on mice, rats, rabbits, occasionally dogs or monkeys (animal models);<\/li>\n
  • mechanistic hypotheses deduced from these two categories.<\/li>\n<\/ul>\n

     <\/p>\n

    Human clinical trials, the well-conducted, randomized, double-blind ones with large sample sizes, are\u00a0rare<\/strong>, and in most cases absent altogether. For many of the most hyped peptides, there isn't a single decent human clinical trial. For others, there are one or two, on a small number of participants, retrospective.<\/p>\n

    Furthermore, essential data is missing to use them judiciously: standardized dosages, optimal treatment duration, long-term safety profiles, and interactions.\u00a0Stated more directly: we don't know what dose, how often, and for how long they should be taken to achieve the maximum theoretical benefit. We don't know the interactions with other drugs or supplements, we don't know the long-term risks, we don't even know what happens in specific populations: pregnant women, the elderly, people with pre-existing conditions.<\/strong><\/p>\n

     <\/p>\n

    In addition to this, there is a structural problem with the market: most of these peptides are not legally approved for human use, and therefore do not go through regular pharmaceutical channels. They are found on independent websites that legally protect themselves by selling the product as \u201cfor research purposes only\u201d and \u201cnot for human consumption.\u201d In practice, this means there's no serious control over quality, purity, contamination, or actual dosage. The vial you receive might contain the declared molecule in the declared quantity. Or the right molecule at a completely different concentration. Or something else entirely. Impurities also matter: they can be responsible for side effects, skin rashes, allergic or pseudo-allergic reactions completely independent of the peptide itself.<\/strong><\/p>\n

     <\/p>\n

    So when a peptide is sold to you as \u201crevolutionary, safe, effective,\u201d the most honest translation is: \u201cinteresting in theory, plausible mechanistically, but in practice, today, we know almost nothing about how it actually behaves in you.\u201d.\u00a0In the most optimistic scenario, it works as theory suggests. In an intermediate scenario, you don't feel anything at all and have just wasted money. In the worst-case scenario, you end up with side effects and none of the benefits.<\/strong><\/p>\n

     <\/p>\n

    Where does the average effect really fit in?<\/strong><\/h3>\n

    It must be said immediately:\u00a0There is a small number of peptides that, even today, seem to work in a fairly predictable and consistent manner. They are a minority compared to the vast number of products sold on independent sites, but they exist, and the anecdotes collected from users converge quite neatly. As always, there are exceptions in both directions: people for whom the effect is more pronounced than expected, and people for whom it falls short of expectations. But the underlying signal is recognizable.<\/strong><\/p>\n

    One thing worth stating clearly, because you'll hardly find it in a popular science article. Having frequented communities that truly discuss peptides for a long time (forums, private groups, coaching, Reddit, dedicated Facebook groups, industry Instagram pages, where people share their real-world experiences), the impression is quite clear: in most cases, the actual effect falls between\u00a0\u201cI absolutely heard nothing.\u201d<\/strong>\u00a0and\u00a0\u201cYes, I sensed something, but much less than I expected.\u201d<\/strong>. The cases where the effect truly matches the theory or even surpasses it are a minority. Cases of only side effects, with no benefit, are also a minority but they exist. In short, the distribution is not what marketing leads one to imagine.<\/p>\n

    It should be said that many of these disappointments do not necessarily depend on the molecule itself. Often, incorrect usage methods, products of uncertain quality, randomly chosen dosages, or a basic lifestyle that isn't producing any signals to amplify come into play. Or The amplification is indeed there, but it's so marginal that it's imperceptible in the short and medium term. And if the effect is so subtle, even in the long term it becomes almost impossible to say how much any improvement is due to the peptide, how much to the new lifestyle, how much to the placebo, and how much to the simple fact that all these things have happened together. <\/strong>When an experimental starting molecule is used in an equally uncertain context, the final result is inevitably difficult to interpret.<\/p>\n

    Obviously, we need to distinguish based on the type of peptide: let's take I as an example\u00a0GLP-1<\/strong>. As we were saying, they are peptide hormones and they produce a direct effect: they act on satiety centers and concretely reduce hunger. People who have lived for years with that constant background noise of hunger and food cravings can finally turn it off and live freely: here the theoretical and practical effect truly coincide, apart from the exceptions that always exist in medicine. For most other wellness peptides, however, the picture is much more nuanced.<\/p>\n

     <\/p>\n

    Why perception often surpasses reality<\/strong><\/h3>\n

    One last element worth mentioning is the role of\u00a0perception<\/strong>. The placebo effect here is particularly strong, for two additional reasons compared to the usual. First: you pay for it, often a lot. When you invest non-trivial amounts of money in a product, there's a natural psychological resistance to concluding that it's not working: the brain looks for signals compatible with the investment. Second: there's the gesture of the injection itself, which carries its own almost ritualistic aura, something \u201cmore serious\u201d and \u201cmedical\u201d than a pill, and this amplifies the expectation of a visible result.<\/p>\n

    In addition to this, there is a curious but widespread logical fallacy. Many peptides are\u00a0prohibited by WADA<\/strong>, the World Anti-Doping Agency. For some of the public, this is read as proof of effectiveness:\u00a0\u201cIf they banned them, then it really works, otherwise they wouldn't have bothered.\u201d<\/em>. It's a line of reasoning that sounds logical, but it's tricky: WADA includes many substances on its lists that are \u201cnot approved\u201d for medical use, even if only because they are potentially doping substances on paper, and regardless of whether there is real clinical evidence of their efficacy. Being on WADA's blacklist says something about\u00a0theoretical potential<\/strong>\u00a0of the molecule, not on its\u00a0Proven efficacy in humans<\/strong>.<\/p>\n

     <\/p>\n

    The parallel with supplements\u00a0<\/strong><\/h3>\n

    I find the most useful way to understand the situation is to compare it to that of certain supplements many of us are familiar with.<\/p>\n

    Lo\u00a0zinc<\/strong>\u00a0It's a perfect example. It's an essential enzyme cofactor for testosterone production, thyroid function, the immune system, and hundreds of other processes. It's a fundamental nutrient for male hormonal health.<\/p>\n

     <\/p>\n

    What does it mean in practice?<\/h4>\n
      \n
    • If you are deficient in zinc, supplementing it really helps. You correct a real deficit, and biological parameters improve measurably.<\/li>\n
    • If your levels are normal, supplementing with zinc won't push your testosterone to supra-physiological levels. You won't become Superman. You're simply ensuring the machine has enough fuel to do what it was already doing.<\/li>\n<\/ul>\n

       <\/p>\n

      The peptides<\/strong> On paper, they function similarly. They can optimize, they can amplify, they can give a small advantage if the system is already in motion. But they don't replace your lifestyle<\/strong> and they do not produce miraculous transformations in people without a biological signal to amplify.<\/p>\n

       <\/p>\n

      In summary<\/strong><\/h3>\n

      Peptides are a real biological class<\/strong>, important and with extraordinary theoretical potential. Many of them could one day become frontline drugs for problems we currently manage poorly: aging, sarcopenia, chronic injuries, metabolic and degenerative diseases.<\/p>\n

      But today, in 2026, We are still predominantly in the promise phase, not the proof phase<\/strong>. The distance between \u201cthe mechanism is elegant\u201d and \u201cthe clinical study shows it works\u201d is precisely the distance that separates science from marketing.<\/p>\n

      The takeaway message is simple: Peptides are neither the absolute evil nor the revolution<\/strong>. I am\u00a0signal amplifiers<\/strong>, and amplifying zero always gives zero. Lifestyle: training, nutrition, circadian rhythm, stress management, and so on remains the foundation. If that foundation is there, some well-chosen, high-quality peptide might add something. If it's not there, no peptide in the world will build it for you.<\/p>\n

       <\/p>\n

      I would like to know what you think. Had you heard about peptides before?<\/strong><\/p>\n

      Did you have the idea that they were something completely different from what I described here?<\/p>\n

      Tell me in the comments<\/strong>, I'm curious to read concrete experiences, doubts, or even just immediate opinions.<\/p>\n

      Thank you for your time and willingness to delve deeper.<\/p>\n

      Oliver<\/strong><\/p>","protected":false},"excerpt":{"rendered":"

      Cosa sono davvero i peptidi e perch\u00e9 la maggior parte di quello che senti dire \u00e8 inesatto Negli ultimi due anni i peptidi sono diventati il tema caldo della medicina del benessere. Li trovi nei podcast di longevit\u00e0, nei reel di biohacking, nei protocolli di atleti famosi. Promettono di bruciare grasso senza muoverti, riparare tendini […]<\/p>\n","protected":false},"author":7,"featured_media":32008,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"categories":[178,1],"tags":[],"class_list":["post-32004","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-benessere","category-non-categorizzato"],"_links":{"self":[{"href":"https:\/\/cristinatomasi.com\/en\/wp-json\/wp\/v2\/posts\/32004","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cristinatomasi.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cristinatomasi.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cristinatomasi.com\/en\/wp-json\/wp\/v2\/users\/7"}],"replies":[{"embeddable":true,"href":"https:\/\/cristinatomasi.com\/en\/wp-json\/wp\/v2\/comments?post=32004"}],"version-history":[{"count":0,"href":"https:\/\/cristinatomasi.com\/en\/wp-json\/wp\/v2\/posts\/32004\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/cristinatomasi.com\/en\/wp-json\/wp\/v2\/media\/32008"}],"wp:attachment":[{"href":"https:\/\/cristinatomasi.com\/en\/wp-json\/wp\/v2\/media?parent=32004"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cristinatomasi.com\/en\/wp-json\/wp\/v2\/categories?post=32004"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cristinatomasi.com\/en\/wp-json\/wp\/v2\/tags?post=32004"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}