What Actually Slows How Fast You Age, and What the Evidence Says About the Things You Are Sold

In short

Nothing available to any human being has been shown to undo ageing, and no drug, supplement, drip or hormone has been shown in a trial to slow human ageing itself. What the published evidence does support is changing how fast decline happens, and the list is short and unglamorous: not smoking, with quitting before 40 removing about 90% of the excess risk of death from continued smoking (Jha et al., NEJM 2013); cardiorespiratory fitness, where the fittest group had an adjusted all-cause mortality hazard ratio of 0.20 against the least fit (Mandsager et al., JAMA Network Open 2018); 150–300 minutes a week of moderate activity plus muscle-strengthening work on at least two days (WHO 2020 guidelines; Momma et al., Br J Sports Med 2022); control of blood pressure, blood glucose and LDL cholesterol; around seven hours of sleep; and correcting hearing and vision. Roughly 45% of dementia worldwide is attributed to 14 modifiable risk factors, including hearing loss, high LDL cholesterol, hypertension, diabetes, smoking, inactivity, depression, social isolation and untreated vision loss (Lancet Commission on dementia, 2024). The commonest wrong assumption is that persistent tiredness in your thirties is ageing: it is far more often vitamin D or B12 deficiency, iron-deficiency anaemia, an undiagnosed thyroid disorder, obstructive sleep apnoea or depression, each of which is a diagnosis rather than a decade. Products sold as slowing ageing have generally either failed their trials or never been tested against any clinical outcome, and technical noise alone has produced deviations of up to nine years between replicate measurements of the same sample across six prominent research epigenetic clocks (Higgins-Chen et al., Nature Aging 2022). This page is general health information drawn from published evidence. It is not an offer of treatment, it recommends no drug, hormone or supplement, and it is not a substitute for seeing a doctor. Written and reviewed by Dr. A. Ameer Jahan, MBBS, MD, TNMC 28017, AJ Subaitha Medical Centre, Egmore, Chennai, reviewed 15 August 2026.

At what age does ageing start?

There is no single switch and no single age. Different systems start changing at different times, at different speeds, and the change is measurable long before anything is noticeable. Asking "when does it start" produces a misleading answer; asking "what is changing now, and how fast" produces a useful one.

The table below is organised by system rather than by birthday. Each row is the earliest point at which change is reliably measurable in published data, not the point at which a person feels it.

Can ageing be undone?

No. No intervention has been shown to undo ageing in a human being, and no trial has demonstrated it. Claims of having taken years off a person's age generally come from single unblinded self-experiments measured on tests whose measurement error is wider than the effect being claimed, and scientists working in the field have said publicly that such results are being misrepresented.

The distinction that matters is between undoing something and changing its rate. Rate can be changed, and the evidence for that is solid. A person who is fit, not smoking, with controlled blood pressure and glucose, sleeping adequately and hearing and seeing properly declines more slowly than a person who is not. That is a real finding with large effect sizes behind it. It is not the same claim as restoration, and any page that blurs the two is selling something.

It is also worth naming what the science actually says when it is quoted at you. The twelve hallmarks of ageing (López-Otín et al., Cell 2023) are a research framework, and the authors' own criteria for inclusion were established largely in laboratory organisms. Naming a hallmark, naming a molecule that touches it in a cell line, and implying a benefit to a person is the commonest move in this market, and it is not evidence.

What actually slows how fast you age?

The honest answer is a short list of ordinary things that have been tested against death and disease rather than against a laboratory marker. Nothing on the list is a product, and none of it is new.

Read the list as a whole rather than row by row. These are risk factors, not treatments, and every one of them is a matter of ordinary living rather than of anything bought. That is the comparison every product discussed further down this page is being measured against.

How much exercise does the evidence actually support?

Two separate things are being measured here and they are not interchangeable. Aerobic activity and muscle-strengthening work each carry independent mortality associations, which is why the guidelines ask for both rather than letting one substitute for the other.

One measurable number is worth knowing because it replaces guesswork. Cardiorespiratory fitness measured on a treadmill predicted death more strongly than smoking, hypertension or diabetes in the Cleveland Clinic cohort of 122,007 patients (Mandsager et al., 2018), which is an unusual finding for any single measurement to produce. One honest caveat applies to all of it: these dose-response curves come overwhelmingly from American, European, East Asian and Australasian cohorts, and India's metabolic baseline differs enough that transferring them exactly is an assumption rather than a finding.

Why am I always tired at 30? Is that ageing?

Almost never. Fatigue is one of the commonest reasons adults consult a general outpatient clinic anywhere, and the list of things that explain it is a list of diagnoses, not decades. Ageing does not produce sudden, persistent, months-long exhaustion in an otherwise healthy person in their thirties; something else usually does.

Vitamin D deficiency is the largest single candidate in this country, though the size of the problem is easy to overstate. The most widely quoted Indian figures — 46.5% deficient and a further 26% insufficient across 2.2 million test results between 2019 and January 2025, with South India the most affected region at 51.6% — come from a commercial pathology dataset published by Metropolis Healthcare Limited in 2025. Those are test results from people who presented for testing, so they describe how often deficiency is found on testing, not how common it is in the Indian population, and the true population figure is likely to be lower. B12 deficiency is common on predominantly vegetarian diets. Iron-deficiency anaemia, undiagnosed hypothyroidism, obstructive sleep apnoea and depression complete the list, and every one of them is identifiable and treatable.

What follows from that is unremarkable and useful: fatigue that has lasted more than a few weeks is a reason for an ordinary consultation and a small number of ordinary blood tests. It is not a reason for an infusion, a panel of novel markers or a supplement bought on the strength of a symptom. A deficiency that has been measured can be corrected under medical supervision; a deficiency that has been assumed usually cannot.

Do you lose muscle after 40, and can you stop it?

Muscle mass falls at roughly 1–2% a year from the mid-thirties, and strength falls faster than mass does (Indian Consensus on Sarcopenia, 2025). In India the consequences arrive earlier than most people expect. A 2024 cross-sectional study in western India found sarcopenia in about 10% of middle-aged adults, with 4.2% severe (PLOS Global Public Health, 2024).

Inadequate protein intake was an independent risk factor in that Indian data. That is a dietary pattern question rather than a supplement question, the evidence sits with total daily protein from ordinary food alongside resistance training, and it is stronger than the evidence behind anything named in the section below.

The practical significance is not appearance. Muscle strength and cardiorespiratory fitness are the two measurable capacities that track most closely with independence in later decades, and resistance work is the intervention shown to move them. Someone who is thin but weak, the pattern often described as thin-fat, with normal body weight and high truncal fat — is not protected by the number on the scale, and abdominal obesity affects 39.5% of Indian adults against 28.6% with generalised obesity (ICMR-INDIAB-17, 2023).

How do I protect my memory as I get older?

Asked as a memory question, this is answered as a blood-vessel and sensory question. The 2024 Lancet Commission attributes about 45% of dementia worldwide to 14 modifiable risk factors: low education, hearing loss, high LDL cholesterol, depression, traumatic brain injury, physical inactivity, diabetes, smoking, hypertension, obesity, excessive alcohol, social isolation, air pollution and untreated vision loss. Vision loss and high LDL were the two added in 2024.

So the evidence-based answer to "how do I protect my memory" is that hearing and vision should be tested and corrected, blood pressure and lipids and glucose should be controlled, activity should be maintained, and depression and social isolation should be taken seriously. None of that is a memory intervention in the way the market uses the phrase, and all of it has outcome data behind it.

Two honesty markers belong here. The ACHIEVE trial of hearing intervention was null in its overall population and positive only in a pre-specified higher-risk subgroup, so hearing correction is clearly worth doing for hearing and remains promising but unproven for cognition. The cataract-surgery finding is observational, and confounding by health-seeking behaviour is entirely plausible.

One further finding is reported here because readers encounter it and because it is frequently overstated. A natural experiment using the age cut-off for eligibility in a national zoster vaccination programme found new dementia diagnoses reduced by 3.5 percentage points in absolute terms, a 20.0% relative reduction over seven years (Eyting et al., Nature 2025). No randomised trial has tested dementia as an endpoint, the mechanism is unknown, and quasi-experimental designs of this kind establish an association under assumptions rather than an effect. Nothing on this page recommends any vaccine or any other product; immunisation is a decision for a person and their own doctor.

Ordinary forgetfulness that the person notices themselves is usually not dementia; memory change that family members notice is a different matter and is covered in the closing section.

Do Indians age faster than people in the West?

On the measures that can actually be compared, the useful observation is not that ageing runs faster but that the metabolic conditions which shape later decades are extraordinarily common, and mostly silent when they first appear.

ICMR-INDIAB-17 (Lancet Diabetes & Endocrinology 2023), which surveyed 113,043 adults across 31 states and union territories, is the baseline every reader in Chennai is standing on: 11.4% diabetes, 15.3% prediabetes, 35.5% hypertension, 28.6% generalised obesity, 39.5% abdominal obesity and 81.2% dyslipidaemia. Those are the conditions that determine how the next three decades go, and most of them produce no symptoms at the point when they could most usefully be found.

The demographic backdrop is changing at the same time. India's population aged 60 and over is projected to reach 20.8% by 2050 (UNFPA India Ageing Report, 2023). For a reader in Chennai the realistic goal is fewer years spent ill, and the window in which that is decided opens earlier than most Western health content assumes.

Why do I look older than my age?

One exploratory study of 202 Indian women, graded by 693 assessors, found that observers over-estimated their ages and that the drivers differed by decade: skin lightness parameters dominated in the thirties, while from the forties onward wrinkles around the eye area, the glabella and the corners of the mouth were also drivers (Cosmetics, 2018). That study was conducted by a cosmetics company, and this article treats funding source as material elsewhere, so it is reported here with the same qualification: it is a single industry-funded observational study, not a settled finding.

The modifiable inputs are cumulative ultraviolet exposure, smoking and sleep. The only randomised trial of sunscreen against skin ageing found that daily use of SPF 15 or higher on the head, neck, arms and hands produced 24% less skin ageing on microtopography grading over 4.5 years compared with discretionary use (Hughes et al., Annals of Internal Medicine 2013). Two qualifiers are part of the finding rather than footnotes to it: the trial showed slowed accumulation and not removal of existing photoageing, and the same trial's beta-carotene arm showed no effect on photoageing at all.

Beyond that, skin is a dermatology subject. An assessment of pigmentation, texture or any cosmetic question belongs with a dermatologist rather than with further reading here.

At what age does menopause start in India?

This section reports published evidence only and contains no clinical direction; it sits outside the author's registered field and any decision belongs with a gynaecologist.

The clinical relevance of the age is not cosmetic. Bone resorption is fastest in the first three to four years after menopause, and cardiovascular risk changes after it, so the age at which menopause occurs sets when both clocks start (Indian Menopause Society guidance, 2019–2020). Menopausal hormone therapy is a treatment for menopausal symptoms and for bone loss and is not a treatment for ageing; published positions hold that for most healthy symptomatic women under 60 and within ten years of menopause the benefit-risk balance is favourable (NAMS position statement, 2022). Which is to say it is a consultation, not a decision to be made from a search result.

What about NAD+, NMN, collagen, stem cell therapy, IV drips and the rest?

Most people asking this were told these things work by someone they trust, and often by someone with no financial interest at all. The reason to go through them one by one is not to sneer but because the underlying error is the same each time: a product moves a marker in a laboratory, and the marketing treats that as though it moved the person.

It is worth knowing what Indian law permits a supplement to claim, because the claim on the packet is frequently unlawful rather than merely unproven. The FSS (Advertising and Claims) Regulations 2018 bar any claim that a food is suitable for preventing, alleviating, treating or curing a disease unless specifically permitted, and the FSS (Health Supplements, Nutraceuticals, Food for Special Dietary Uses, Food for Special Medical Purpose, Functional Food and Novel Food) Regulations 2016 bar labelling or presentation claiming the property of preventing, curing or treating a human disease. A reader who knows that is better protected than one given a list of products.

No supplement, hormone, drug, drip or therapy is recommended anywhere on this page, and that is deliberate rather than an omission. Where a substance is named above, it is named in order to report what a trial found.

Is a biological age test worth doing?

These tests measure DNA methylation at selected sites and run it through a model trained to predict either chronological age, a mortality-and-biomarker composite, or a rate of change. They do not measure a single underlying biological quantity, and the number returned is a model output rather than a fact about the body.

The reproducibility problem is the one to understand before paying for one. Technical noise alone produced deviations of up to nine years between replicate measurements of the same sample across six prominent research epigenetic clocks (Higgins-Chen et al., Nature Aging 2022). Retraining those clocks on principal components brought most replicates to within about 1.5 years, but consumer tests do not necessarily use the retrained versions. A result that improves by four years after three months of effort therefore sits comfortably inside the measurement noise, and a repeat test on the same blood could return a materially different number.

The expert consensus statement on biomarkers of ageing (Journals of Gerontology Series A, 2024–2025) frames these markers as outcome measures for intervention research rather than as clinical tests, and no consensus exists on which combination is most useful. Nobody has yet shown that an intervention which moves one of these clocks thereby changes whether a person develops disease or when they die. CALERIE — 25% caloric restriction prescribed for two years in 220 non-obese adults, with approximately 12% restriction actually achieved and about 10% weight loss — slowed one pace-of-ageing measure by roughly 2–3% with no significant change in two others (Waziry et al., Nature Aging 2023).

What tests make sense at 40?

The useful list is short, boring, and made up of measurements with outcome evidence behind them, which is precisely what distinguishes it from a large novel panel. Everything below is ordinary and is interpreted in an ordinary outpatient consultation rather than as a package.

What is not on the list is as informative as what is. Epigenetic age panels, broad micronutrient screens in people with no symptoms, and inflammatory-marker packages sold as ageing assessments have no outcome evidence supporting their use as clinical tests in a well adult, and an abnormal result on a test that should not have been ordered generates anxiety and further testing rather than information.

Short answers to the questions that usually come next

Does intermittent fasting slow ageing?

In humans, fasting protocols produce weight loss comparable to equivalent calorie restriction, and there is no human lifespan data at all. The excitement comes from rodent lifespan studies, and the gap between a mouse and a person is the same gap that undermines the supplement claims above. If it helps someone eat less overall, that is a reasonable use of it; it is not an ageing intervention.

How many hours of sleep do I need?

Around seven. Relative to seven to eight hours, sleeping under seven carried a pooled hazard ratio of 1.14 for all-cause mortality and nine or more carried 1.34 (meta-analysis, GeroScience 2025), though the long-sleep half of that U-shape is heavily confounded because illness itself causes long sleep. Persistent unrefreshing sleep with snoring or witnessed pauses in breathing points to obstructive sleep apnoea, which is common, treatable, and frequently sitting behind the complaint of feeling old and exhausted.

Can grey hair be brought back to its original colour?

No. Greying reflects loss of pigment-producing melanocytes in the hair follicle, and nothing sold for it has been shown to restore that. B12 deficiency and thyroid disorders are worth excluding when greying is early, because they are treatable conditions in their own right, not because correcting them restores hair colour. Schedule J of the Drugs and Cosmetics Rules 1945 lists premature greying and change in hair colour among the conditions no drug may claim to prevent or cure, so any product making that claim is making an unlawful one.

Do ozone therapy, PRP or similar offerings help?

No such therapy has demonstrated a lifespan or healthspan benefit in humans. The Advertising Standards Council of India's 2024–25 annual complaints report processed 370 healthcare advertisements and found roughly 56% of them misleading, and referred 233 health advertisements to the Ministry of AYUSH for potential breaches of the Drugs and Magic Remedies (Objectionable Advertisements) Act 1954. That is a reasonable indication of how much of what is advertised in this space survives scrutiny.

How do I know if this is ageing or something is actually wrong?

Ageing is gradual, symmetrical and does not usually announce itself over a few weeks. The findings below are not ageing. Any one of them is a reason for assessment rather than for waiting to see whether it settles, and the third column names the kind of clinician who ordinarily assesses it.

A sensible check for an adult in their forties in Chennai is the short list in the section above, interpreted by a doctor who knows the family history, in a consultation rather than as a package. The things with evidence behind them for how fast a person declines are activity of both kinds, not smoking, controlled blood pressure and glucose and lipids, adequate sleep, corrected hearing and vision, enough protein, and other people. If anything in the table above describes you, that is a reason to see a doctor now rather than to wait.

About this article

Written and clinically reviewed by Dr. A. Ameer Jahan, MBBS, MD, Chairman and Senior Consultant — Reproductive Medicine, Male Infertility and STD, TNMC registration 28017, at AJ Subaitha Medical Centre, Egmore, Chennai. Reviewed 15 August 2026. Sections on menopause, dementia risk, sarcopenia and skin fall outside the author's registered field and are reported strictly as cited published evidence, with no clinical direction; those decisions belong with the relevant specialist.

AJSMC is an outpatient and day-care multi-speciality centre in Egmore, Chennai. It has no ageing, wellness, longevity or hormone-optimisation service, and this article does not describe one. This page is patient education. It describes what published research has found, it recommends no product, drug, hormone, supplement or procedure, and it is not an offer or description of any service. It is not a substitute for individual medical advice.

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