Written and medically reviewed by Dr. Daniel Chong. Last reviewed 2026-11-13. 16 min
By Dr. Daniel Chong · Human Performance and Longevity, AOKLINIK
Healthy skin often starts with what is happening inside the body. Hormonal balance and metabolic health play a quiet but important role in how skin looks and behaves, which is why focusing on the surface alone may not tell the full story.
I want to be careful with that sentence, because it is one step away from a much worse one. "Heal your skin from within" is the opening line of a great deal of nonsense, and the supplement industry has made the idea of internal causes faintly embarrassing to discuss seriously.
So this article tries to do two things. Set out where the connection between skin and internal health is genuinely well established, which is further than most patients realise. And say plainly where it is not, which is most of what is sold on the strength of it.
Why the surface sometimes cannot answer the question
A patient comes in about her skin. It is duller than it was, drier, the texture has changed, fine lines have appeared faster than the last few years would explain. She has been treating it conscientiously from the outside.
There are two possibilities and they look identical on the surface. Either this is the ordinary accumulation of time and sun, which is a surface problem with surface answers. Or something has changed internally and the skin is reporting it.
The skin is unusually good at reporting, for a reason worth knowing: it is visible. The same process happening in a blood vessel wall or a tendon produces no symptom you would notice for years. In skin you see it in the mirror. That makes skin an early and rather sensitive readout of several internal processes, which is useful if you read it as information rather than only as a complaint.
The practical consequence is simple. If we treat the surface and the cause is internal, the result is worse and shorter-lived than it should be, and the patient concludes that treatment does not work on her. It did. It was asked the wrong question.
Glycation: the clearest link between metabolism and skin
If there is one mechanism to understand here, it is this one, because the biochemistry is settled and it explains a great deal.
Sugars in the bloodstream react with proteins directly, without an enzyme involved. This is the same chemistry that browns food, and it happens slowly and continuously in the body. The products are called advanced glycation end-products.
Why skin is particularly affected. This reaction accumulates in long-lived proteins, because the longer a protein sits in the body, the more opportunity it has to be modified. Most proteins are replaced within days or weeks. Dermal collagen and elastin are among the longest-lived structural proteins you have, turning over across years rather than days.
So they accumulate this damage in a way that a liver enzyme never does.
What it does. The reaction forms cross-links between collagen fibres. Cross-linked collagen is stiffer, less elastic, and harder for the body to break down and replace, which is the normal maintenance process. The result is skin that is less resilient and less able to remodel itself. Glycated proteins also bind a specific cell-surface receptor that drives inflammatory signalling, so there is an inflammatory component as well as a mechanical one.
What follows from it, and this is the useful part. The rate of this process depends on how much sugar is circulating and for how long. That is not a statement about whether you ate dessert. It is a statement about average glycaemic exposure over years, which is precisely what metabolic health is.
Two people the same age with the same sun exposure and meaningfully different average blood glucose over two decades are not accumulating this damage at the same rate. That is a real difference, it is cumulative, and it is invisible until it is not.
And the honest limits. The biochemistry being solid does not mean the interventions are. Topical and oral products sold as anti-glycation are not well supported by human outcome evidence, and I would not spend money on them. Dietary glycation products, from food browned at high dry heat, are frequently discussed, and their contribution relative to the body's own production is less clear than the marketing suggests.
What is well supported is unglamorous: glycaemic control, through the ordinary means of diet composition, body composition and physical activity. Which is the same advice as for the rest of your health, and that is rather the point of this article.
Oestrogen, and what happens to skin around menopause
Skin carries oestrogen receptors. It is a hormonally responsive organ, not merely a covering.
When oestrogen declines, several things change together: collagen content falls, the dermis thins, the skin holds less water, elasticity reduces, and wound healing slows. Many women describe the change as sudden, and in the sense that it is faster than the preceding decade, that perception is reasonable.
On the figure you have probably read. You will see it stated that women lose thirty per cent of skin collagen in the first five years after menopause. It is quoted constantly, including by clinics. The direction is not in doubt. The specific figure traces back to small and methodologically limited older work, and whether a decline of that magnitude and timing is real is contested rather than settled.
I mention it because the figure is used to sell things, and because a patient who later discovers the number was shaky may reasonably wonder what else she was told. The honest version is that the change is real, it is meaningful, and nobody can give you a reliable percentage.
What this means practically. It means the skin of a woman in her early fifties may be behaving differently from how it behaved at forty-five for reasons that have nothing to do with her skincare, and that treating it with the same expectations will disappoint her.
It also means her skin is one of several things changing at once, and the skin conversation is often the one that brings her in. If sleep, body composition, bone and cardiovascular risk are also shifting, those matter more, and the consultation should not end at her face. We have written separately on this stage of life and on the evidence around hormone therapy, which is a medical decision with risks and benefits rather than a skin treatment and should never be framed as one.
Androgens, insulin, and acne after thirty
Adult acne is where internal causes are most often missed, and most often treatable.
Sebaceous glands respond to androgens. That is not a theory, it is how the gland works. Where androgen activity is raised, the glands produce more sebum and the skin behaves more like adolescent skin. This is why adult acne frequently does not respond to the things that work on teenage acne.
Insulin is part of the same picture. Insulin and insulin-like growth factor increase sebum production and the proliferation of the cells lining the follicle. So insulin resistance and acne travel together more often than coincidence would explain, which is also why acne, irregular cycles and difficulty with weight frequently appear in the same patient.
Androgen excess has several causes, polycystic ovary syndrome among them, and distinguishing them requires history, examination and the right tests rather than assumption. That is a medical assessment, and it is a different conversation from choosing a facial.
Why this matters for how it is treated. If adult acne is being driven by something hormonal or metabolic, treating only the skin means managing it indefinitely rather than addressing why it is happening. Both have a place, and the surface treatments work better when the driver is dealt with.
Thyroid: the one that looks like ageing
Worth its own mention because of how often it is attributed to getting older.
An underactive thyroid produces dry, coarse skin, a sallow quality, thinning hair, sometimes loss of the outer part of the eyebrow, and a general puffiness. An overactive one produces warm, moist skin and fine, thinning hair.
Patients present with these as skin and hair complaints and describe them as ageing. It is one of the simpler things to check, one of the more treatable things to find, and it will not respond to anything applied to the surface.
Cortisol, sleep and the barrier
Psychological stress measurably delays recovery of the skin barrier. That is not a wellness assertion, it has been demonstrated experimentally.
A compromised barrier means more water loss, more sensitivity, more reactivity to products that were previously fine, and slower settling after treatment. Patients describe their skin as having become sensitive, and frequently the skin has not changed in character so much as lost its ability to recover.
Sleep sits alongside this, and it shows first around the eyes, which I have written about at length. What I would add here is that the periorbital appearance patients most want treated is often the most responsive to something free.
When the skin is reporting something you should investigate
Some skin findings are not cosmetic concerns at all. They are signs, and recognising them is one of the more useful things a doctor can do during an aesthetic consultation.
Velvety darkening and thickening in the skin folds, typically at the neck, armpits or groin, is a recognised sign of insulin resistance. Patients often arrive asking to have it lightened. Treating the pigment without investigating the cause misses the point of it entirely.
Multiple skin tags, particularly appearing in numbers around the neck and trunk, are associated with the same picture. Dr. Kamen has written separately on the skin signs she looks for during an aesthetic consultation.
Hair shedding can reflect iron status, thyroid function, recent illness, rapid weight loss or several other things, which is why it warrants assessment before treatment. The evidence linking iron stores to shedding is less clear-cut than it is often presented, which is itself a reason to measure rather than assume.
A sudden, marked change in skin or hair without an obvious cause deserves a doctor's attention rather than a treatment plan.
Where an assessment turns up something that needs medical management, that is a medical consultation and it should be handled as one. It is not an aesthetic package, and it is not something to be sold alongside one.
What this does not mean
This is the section that makes the rest of the article trustworthy, because every claim above has been used to sell something it does not support.
It does not mean your skin problem is a hormone problem. Most skin complaints are what they appear to be: sun damage, genetics, time, an unsuitable product, a dermatological condition. Internal causes are worth considering, not assuming, and a clinic that finds a hormonal explanation for every patient is not assessing, it is marketing.
It does not justify a large hormone panel. Hormones vary with time of day, cycle phase, illness, stress and sleep. A result without a clinical question behind it produces an abnormal-looking number that leads to more tests and no decision. Tests should be chosen because the answer changes what we do.
It does not mean supplements fix it. Most products sold for hormonal balance or skin from within are not supported by human outcome evidence. Collagen supplements have some positive trials and a great deal of industry funding behind them, and I would describe the evidence as genuinely unsettled rather than either proven or worthless.
It does not mean food intolerance testing is useful. Those panels generate long lists of foods, anxiety, and unnecessary dietary restriction. They are not a diagnostic tool for skin disease.
And there is no detox involved. Your liver and kidneys perform that function and they do not require purchased assistance.
It also does not mean the surface does not matter. Sun protection remains the single highest-yield thing you can do for how your skin looks in twenty years, and nothing internal substitutes for it. Our article on sun protection in this climate covers that.
Internal and external are not competing explanations. Treating only one of them when both apply is the error, in either direction.
How this works in practice at AOKLINIK
Aesthetic medicine and longevity care operate side by side here, and the reason is the overlap described above rather than a marketing convenience.
Every plan begins with a clinical assessment, so that it reflects your individual biology rather than a template. In practice that means a history, an examination, and a small number of tests chosen because the result would change a decision. Not a large panel because it looks thorough.
The assessment decides which problem we are solving. Sometimes the answer is entirely aesthetic and nothing internal is relevant, and we say so rather than manufacturing a longevity conversation. Sometimes what the patient came in about is a sign of something else, and that changes the order of things. Often both apply, and the sequencing matters: surface treatments perform better, and last longer, when the thing driving the problem has been addressed.
And sometimes the honest answer is fewer treatments than expected, or none, with a review date. That is a legitimate outcome of an assessment rather than a failure of one.
The short version
Skin is a visible readout of several internal processes, which makes it an early signal rather than only a surface to be treated.
Glycation is the clearest mechanism. Sugars react with long-lived proteins, dermal collagen and elastin are among the longest-lived you have, the resulting cross-links make them stiffer and harder to remodel, and the rate depends on average glycaemic exposure over years. The biochemistry is solid, the products sold against it are not.
Oestrogen decline genuinely changes skin. The thirty per cent in five years figure that circulates is not reliable, and the change is real without it.
Adult acne is frequently driven by androgen activity and insulin, which is why it does not respond to teenage acne treatment. Thyroid disease regularly presents as skin and hair complaints attributed to age. Some skin findings, particularly velvety darkening in the folds and multiple skin tags, are signs worth investigating rather than pigment to be treated.
None of this justifies a large hormone panel, a supplement regime, food intolerance testing or a detox, and none of it replaces sun protection.
Every plan begins with an assessment, because which of these applies to you is a clinical question rather than a marketing one.
Book an assessment
If your skin has changed faster than you can explain, or a treatment that should have worked did not, the useful question is whether we are treating the right problem.
Book a consultation with Dr. Daniel Chong at AOKLINIK Penang.
References
- Wang Y, et al. The effects of advanced glycation end-products on skin and potential anti-glycation strategies. Experimental Dermatology. 2024 onlinelibrary.wiley.com
- Haykal D, et al. Skin glycomics: unmasking the role of glycation end products in cutaneous aging and dermatology. Journal of Cosmetic Dermatology. 2026 pubmed.ncbi.nlm.nih.gov
- Advanced glycation end products promote melanogenesis through the receptor for AGEs. Scientific Reports nature.com
- Kamp E, et al. Menopause, skin and common dermatoses. Part 2: skin disorders. Clinical and Experimental Dermatology. 2022 onlinelibrary.wiley.com
- Skin, hair and beyond: the impact of menopause. Climacteric. 2022 tandfonline.com
- Managing menopausal skin: a clinician's review. European Medical Journal emjreviews.com
- Beyond hot flashes: understanding and treating menopause-associated skin changes. Journal of Integrative Dermatology jintegrativederm.org
Frequently asked questions
Only if there is a clinical reason, which the consultation establishes. A panel ordered without a question usually produces a borderline result and no useful action. If your history and examination point somewhere, testing is valuable.
It may, and I would be cautious about promising it. Better glycaemic control, better sleep and better body composition plausibly slow some of the processes described here and will certainly improve things that matter more than your skin. What I will not tell you is that it reverses existing change, because it does not.
A reasonable suspicion, and the test is whether the clinic ever concludes that nothing internal is relevant. We do, frequently. If every aesthetic consultation you have ever had produced a recommendation for extensive testing, that pattern is telling you something.
A history including your cycle if relevant, medications, and what has already been tried. An examination of the pattern and distribution, which is informative. Then tests only if something points that way. The point is to establish whether something is driving it, because that changes the treatment rather than merely adding to it.
At the level of overall dietary pattern and glycaemic load, plausibly yes, and the mechanisms above are reasonable. At the level of individual foods causing individual breakouts, the evidence is much weaker than the internet suggests. Chocolate has been studied and largely exonerated.
It is a medical decision about risks and benefits across your whole health, and skin should not be the reason for it. There is evidence for effects on skin, and it is not a sufficient indication on its own. That conversation needs a proper assessment.