Cardiorespiratory fitness, body composition, and a few blood markers matter more than most supplements. A practical, evidence based guide to what actually predicts a longer healthspan.
Cardiorespiratory fitness, measured as VO2 max, is one of the strongest predictors of all cause mortality. A meta analysis of 33 studies found that a low level of cardiorespiratory fitness carried a greater risk of death than traditional risk factors like smoking, hypertension, or diabetes. And unlike many risk factors, it is trainable at any age. This single piece of evidence tells you something important about longevity: the most powerful interventions are often the least marketed.
Many people sit in a frustrating gap. On paper they look "fine", with normal bloods, a healthy BMI, and nothing obviously broken, yet they still feel low on energy and clarity. On one side, conventional medicine says "nothing is broken". On the other, the wellness industry offers a thousand things to buy. The science is moving fast, but the hype is moving faster. Patients are stuck in between, trying to make sense of it all on their own.
The five destinations and why they matter
For most people, the goal of longevity medicine is not to chase a single magic metric. It is to steer away from five predictable destinations: cardiovascular disease, neurodegeneration (like dementia), metabolic disease (like type 2 diabetes), musculoskeletal decline (loss of strength and bone), and cancer. Almost all of these have modifiable risk factors. We can act decades before a diagnosis.
This doesn't require a drawer full of supplements or a subscription to the latest gadget. It requires putting effort into the things that move those risks, and ignoring the noise. The evidence is settled on more than you think. A handful of factors account for the bulk of preventable decline. Knowing which is which is half the work.
Proven, promising, experimental: how to filter every claim
Before you act on any longevity claim, run it through three filters.
Evidence: Does it improve a hard outcome (like death, heart attack, or loss of independence), or only a number on a screen? Many interventions improve a biomarker but have zero effect on what actually matters.
Safety: What is the downside? How does it interact with everything else you’re doing or taking? The less studied something is, the more careful you need to be.
Upside: Is the potential benefit actually worth it? Would you recommend it to someone you love? If the risk reward balance is unclear, treat it as experimental, and act accordingly.
Sort everything into three buckets: proven, promising, or experimental. Proven interventions (like exercise and sleep) drive first line care. Promising ones deserve watching. Experimental ones stay optional, supervised, and clearly labelled. Most people invert this, chasing the exotic while neglecting the basics.
Where to start: the cheap, high impact toolbox
Three measures earn their place early, not because they are clever, but because they predict outcomes.
Measure | What it assesses | Why it matters | Evidence strength |
|---|---|---|---|
VO2 max (cardiorespiratory fitness) | How well your body takes in and uses oxygen during exertion | Strong inverse association with all cause and cardiovascular mortality; trainable throughout life | Strong, from multiple large cohort studies |
DEXA scan (body composition) | Bone density, lean mass, and visceral fat | Visceral fat is linked to insulin resistance and metabolic risk; low bone density predicts fracture risk; lean mass relates to physical function | Moderate to strong, depending on outcome |
Targeted blood panel | Lipids, glucose, HbA1c, inflammatory markers (e.g. hs-CRP) | Identifies early metabolic and inflammatory risk that can be modified with lifestyle and, where indicated, medication | Strong for individual markers in combination |
A full cardiorespiratory fitness test, a DEXA scan, and a well chosen blood panel are far more useful than most of what is heavily marketed. They are boring, they are cheap relative to the cost of being unwell, and they give you a baseline you can actually improve. What a “good” score looks like depends on your age and sex. Whether a particular result matters for you is something to discuss with your doctor.
Why I don’t lead with supplements or advanced biomarkers
The hidden cost of the hype is real. False positives, incidental findings, and anxiety generated by testing that was never going to change the plan. There is a valid place for deeper investigation, but it belongs after the basics are in place and still not providing answers. Most people gain more from increasing their fitness, improving their diet quality, and protecting their sleep than from anything sold in a bottle.
The execution problem (and why AI isn’t the answer)
If we already know that movement, sleep, and nutrition matter, why doesn’t it happen? Because the bottleneck is execution, not knowledge. The distance between your good intentions and your actual behaviour at 7pm on a Wednesday, when you are exhausted, is where most plans quietly die.
AI is everywhere in this space, and it is genuinely useful for tracking dynamic risk, supporting clinical decisions, and helping people change behaviour at scale. But it is a tool, not the main character. No amount of data will fix a plan that never gets done. The real work sits in the small, repeated decisions we all find difficult.
From gatekeeper to guide: the role of a doctor today
Patients are no longer waiting for permission to be curious about their health. They arrive in clinic with data from wearables, podcast notes, and internet research. That is a good thing. But in an age of infinite information, the most valuable thing a clinician can offer is not more information. It is trusted interpretation.
The doctor’s role is shifting from gatekeeper to guide. Helping you separate what is proven from what is promising, building a plan rooted in what the evidence actually shows, and making sure the basics are actually being executed. That is not a hard sell. That is just honest medicine.
The goal: not “normal”, but functional
“Normal” is a range, not a target. You can be technically normal on every lab test and still feel exhausted, foggy, and physically fragile. The goal was never to be average for your age. It is strength, clear thinking, resilience, and energy. More years thriving, fewer years declining.
If your only feedback loop is a checklist that says nothing is broken, you miss the opportunity to actually upgrade how you feel. That is the whole aim of an honest longevity approach: close the gap between hype and science, and make the pursuit of a longer healthspan practical, evidence based, and human.
Frequently asked questions
Is VO2 max testing accessible outside of elite sport?
Yes. Lab based testing with a mask and metabolic cart is the gold standard, but many clinics (including sports medicine and longevity focused practices) now offer it. Field based estimates, like the Cooper 12-minute run test, can also provide a reasonable approximation if lab testing is not available. Speak to your doctor about what is appropriate for you.
What is a “good” VO2 max?
There is no single number. Cardiorespiratory fitness declines with age, and what is considered average depends on your age and sex. What matters more than the number is your trajectory, whether you are maintaining or improving it over time. Sitting above the age predicted average is generally protective, but the greatest benefit comes from moving out of the lowest fitness category.
How often should I get a DEXA scan?
It depends on your baseline and goals. For someone with no acute concerns, repeating a DEXA every one to two years can track changes in visceral fat, lean mass, and bone density over time. If you are actively working on body composition or have risk factors for osteoporosis, your clinician might suggest a different interval. This is best discussed in consultation.
Which blood markers matter most for longevity?
A basic panel covering fasting glucose, HbA1c, a full lipid profile (including ApoB and Lp(a) where indicated), and a marker of inflammation like high sensitivity CRP covers a lot of ground. The exact list should be individualised based on your personal and family history. Boring, routine labs, interpreted together, often give you more actionable information than the expensive boutique panels you see online.
An initial consultation is the starting point for discussing which of these measures are right for you. What any result means for your personal risk is something that belongs in a one on one conversation, not a webpage.
General information, not individual medical advice. Speak to your own doctor.
References
Kodama S, Saito K, Tanaka S, et al. Cardiorespiratory fitness as a quantitative predictor of all cause mortality and cardiovascular events in healthy men and women: a meta analysis. JAMA. 2009;301(19):2024-2035.
Ross R, Blair SN, Arena R, et al. Importance of assessing cardiorespiratory fitness in clinical practice: a case for fitness as a clinical vital sign: a scientific statement from the American Heart Association. Circulation. 2016;134(24):e653-e699.
Blair SN, Kohl HW III, Paffenbarger RS Jr, Clark DG, Cooper KH, Gibbons LW. Physical fitness and all cause mortality: a prospective study of healthy men and women. JAMA. 1989;262(17):2395-2401.
Pischon T, Boeing H, Hoffmann K, et al. General and abdominal adiposity and risk of death in Europe. N Engl J Med. 2008;359(20):2105-2120.