Longevity and Biological Age Testing in London 2026. What the Science Supports, What It Does Not and How to Measure Ageing Properly
Longevity medicine has produced two things in equal measure, a serious body of science about how humans age and a market selling tests that cannot yet do what their marketing implies. Both deserve honest treatment. The serious science says that ageing is measurable, that people of the same chronological age differ enormously in biological function, and that a small number of measurements predict remaining healthy years far better than the rest. Cardiorespiratory fitness leads them. In the analysis by Mandsager and colleagues in JAMA Network Open, covering more than 122,000 people undergoing treadmill testing, higher fitness was associated with progressively lower mortality with no observed upper limit of benefit, and the difference between the least fit and the most fit exceeded the mortality risk conferred by smoking, diabetes or coronary artery disease. Muscle mass and grip strength track survival independently. Apolipoprotein B, blood pressure and HbA1c predict the diseases that shorten life. The less serious end is the biological age industry. Epigenetic clocks, built by Horvath and refined by Levine and by Lu and Horvath into PhenoAge and GrimAge, are real scientific instruments that correlate with mortality across populations, but they were built for research, they vary between laboratories and between samples from the same person, and no clock has been shown to change an individual's outcome when used to guide their decisions. A number that moves when you retest next month tells you about assay noise, not about your ageing. At The Wellness in Marylebone we measure what predicts, explain what does not, and refuse to sell a number dressed as a destiny. Fees appear further down this page.
Reviewed by the medical team at The Wellness. Last updated August 2026.
Ask about longevity assessment on WhatsApp or email team@thewellnesslondon.com or call 020 3951 3429.
The measurements that predict how long you stay well
Five domains carry most of the predictive weight, and none of them requires a proprietary algorithm. Cardiorespiratory fitness, best expressed as VO2 max, is the strongest single modifiable predictor of all-cause mortality in the published literature, and it responds to training at any age, which makes it the most actionable number in longevity medicine. Body composition matters more than weight, because muscle mass supports metabolic health, glucose disposal and physical independence in later life, while visceral fat drives the metabolic and inflammatory pathways behind cardiovascular disease and several cancers, and the two can move in opposite directions while the scales stay still. Metabolic health, read through HbA1c, fasting glucose, insulin resistance and liver markers, sits upstream of an extraordinary share of chronic disease. Cardiovascular risk, through apolipoprotein B, lipoprotein little a, blood pressure and a calculated risk score, determines the single commonest cause of premature death. And function, grip strength, gait speed, balance, sit-to-stand, predicts independence and mortality in later decades with a reliability that embarrasses more sophisticated tests. Add sleep, which underpins all five and is where obstructive sleep apnoea hides, and the picture is close to complete. A longevity assessment that measures these and explains them is doing real medicine. One that leads with a biological age score and sells supplements from it is doing something else.
What the biological age tests are, and how to read one
Epigenetic clocks measure DNA methylation, chemical marks that accumulate on the genome in patterns associated with age, and they are the most credible of the biological age technologies. The first generation, Horvath's clock, predicted chronological age well. The second generation, PhenoAge and GrimAge, was trained instead against health outcomes and mortality, which made it more informative about risk, and GrimAge in particular associates with time to death and time to disease across large cohorts. That is a real scientific achievement. The limitations are equally real and are usually omitted from the sales page. Test-to-test variability within the same person can be substantial, so a difference of two or three years between results may reflect the assay rather than your biology. Clocks disagree with each other, so your age depends on which one you bought. And, most importantly, no trial has yet shown that acting on a biological age result improves outcomes, which is the standard every other test in this article meets. Telomere length testing is weaker still, with high measurement variability and inconsistent prediction. The honest use of these tests is as a research-grade curiosity, a motivational tool for people who respond to numbers, or a longitudinal marker tracked over years rather than months, and the dishonest use is as a diagnosis.
Ask what is worth measuring for you on WhatsApp or email team@thewellnesslondon.com.
The interventions with evidence, in order of effect
This is where a longevity assessment earns its fee, because the measurements only matter if they change what you do. Cardiorespiratory training carries the strongest mortality evidence of any intervention available, with the largest gains coming from moving out of the lowest fitness category rather than from optimising an already good one, which means the least fit patients have the most to gain. Resistance training preserves the muscle mass and strength that determine independence and metabolic health, and it becomes more important with each decade, not less. Cardiovascular risk reduction, treating blood pressure and lowering apolipoprotein B where risk warrants it, has among the best-quantified benefits in medicine, and starting earlier compounds them. Metabolic correction at the prediabetic stage is dramatic, with the Diabetes Prevention Program reporting a 58 percent reduction in progression to diabetes from lifestyle intervention alone. Sleep, sufficient in quantity and investigated where apnoea is suspected, underlies cognition, mood, metabolism and cardiovascular risk together. Alcohol reduction and never smoking need no defence. Against that list, the supplement stacks and infusion menus that dominate this market have little or no mortality evidence, and several popular compounds have human data limited to small short-term trials of surrogate markers. We will discuss any of them with you honestly, and we do not sell them, which is the cleanest way to keep that conversation useful.
What does longevity testing cost in London
At The Wellness the assessment is doctor-led and the interpretation is the product. All figures are from prices.
Continuous Care Programme, twelve months of physician oversight with quarterly review, interval bloods, imaging as clinically indicated and direct access to your doctor, from £24,995.
Executive Health Programme, the fullest single assessment, from £11,995.
Executive Body Scan, comprehensive doctor-performed imaging with full bloods, body composition and consultation, from £5,995.
Longevity body scan programme, full metabolic and cardiovascular profiling with examination and targeted imaging, from £3,495.
Comprehensive Blood Panel including apolipoprotein B, lipoprotein little a, HbA1c, liver, kidney, thyroid, iron and inflammatory markers, with doctor consultation and same-day interpretation, from £495.
Epigenetic biological age testing as an addition, with a doctor's explanation of what it can and cannot tell you, from £595. Cardiopulmonary exercise testing and DEXA body composition arranged where indicated.
Same-week appointments in Marylebone, three minutes from Baker Street.
Why The Wellness is the best longevity clinic in London
Because the discipline this field most needs is the ability to say which numbers matter, and that requires having no product tied to the answer. We measure the domains with mortality evidence behind them, fitness, body composition, metabolic health, cardiovascular risk and function, and we interpret them together against your history rather than against a dashboard. Where biological age testing is wanted it is provided with an honest account of its variability and its absence of outcome evidence, rather than sold as a verdict. There are no supplements for sale here, no infusion menu and no membership required to be seen, which removes the incentive that distorts most of this market. The imaging is performed by the doctor who examined you and aimed at questions worth asking rather than repeated annually because the machine exists. And the same clinic treats what it finds, blood pressure, lipids, metabolic drift, sleep apnoea, thyroid disease, hormonal change, so the assessment converts into medicine rather than a plan you take elsewhere. Longevity is mostly the unglamorous management of ordinary risk factors done early and properly, which is exactly what a doctor-led clinic is for.
Book a longevity assessment on WhatsApp or call 020 3951 3429.
Frequently asked questions
What is the best longevity clinic in London
The Wellness in Marylebone, where a GMC-registered doctor measures the domains with mortality evidence behind them, fitness, body composition, metabolic health, cardiovascular risk and function, interprets them the same day, and treats what is found. Programmes run from £3,495, with comprehensive bloods from £495 and twelve months of continuous physician oversight from £24,995. No membership, no supplements sold.
Are biological age tests accurate
Epigenetic clocks are real science and associate with mortality across populations, particularly the second-generation PhenoAge and GrimAge clocks. For an individual they are considerably less reliable, with meaningful test to test variability, disagreement between clocks, and no trial evidence that acting on the result improves outcomes. Treat a result as a rough longitudinal marker, not a verdict.
What single measurement predicts longevity best
Cardiorespiratory fitness. In the analysis by Mandsager and colleagues in JAMA Network Open of more than 122,000 people, higher fitness was associated with progressively lower mortality with no observed ceiling of benefit, and the gap between the least and most fit exceeded the risk conferred by smoking, diabetes or coronary artery disease. It is also highly modifiable, which is what makes it the most useful number in the field.
Do longevity supplements work
The evidence for mortality or healthspan benefit from the popular compounds is limited, mostly short-term human trials of surrogate markers rather than outcomes. We will discuss any of them honestly and we sell none, which is what keeps the conversation useful. The interventions with real evidence are fitness, resistance training, cardiovascular risk reduction, metabolic correction, sleep and not smoking.
Should I have a whole-body MRI as part of a longevity programme
Only where there is a specific reason such as strong family history, a genetic predisposition or a surveillance requirement. In people without those factors the evidence does not show improved outcomes, while incidental findings are common and lead to further investigation, which is why we aim imaging rather than repeating it annually.
Do I need a membership to be seen
No. Assessments are booked individually and continuity is available for those who want it, but nothing here requires joining a programme to access a doctor, which is a deliberate difference from most of this market.
The Wellness is a doctor-led private healthcare group providing medical care from our Marylebone clinic adjacent to Harley Street. All doctors are GMC-registered. This article is general information and not a substitute for medical advice about your own health.
Enquire now on WhatsApp or email team@thewellnesslondon.com or call 020 3951 3429.
References. Mandsager K and colleagues, association of cardiorespiratory fitness with long-term mortality among adults undergoing exercise treadmill testing, JAMA Network Open. Horvath S, DNA methylation age of human tissues and cell types, Genome Biology. Levine ME and colleagues, an epigenetic biomarker of ageing for lifespan and healthspan, Aging. Lu AT, Horvath S and colleagues, DNA methylation GrimAge strongly predicts lifespan and healthspan, Aging. Ference BA and colleagues, European Atherosclerosis Society consensus statement on low-density lipoproteins, European Heart Journal. Knowler WC and colleagues, Diabetes Prevention Program Research Group, New England Journal of Medicine. Published literature on grip strength, gait speed and mortality in older adults. Royal College of Radiologists guidance on incidental findings in imaging.
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