A biological age test tries to estimate how old your body functions, apart from your birth year. Two men of fifty can differ biologically by years. The most reliable measures are not a single blood value, but things like your walking speed, your grip strength and certain patterns in your DNA (Horvath, 2013).
I am honestly sceptical about a lot of what is offered online. "Take this test and know your real age" sounds great, but most free tests measure something quite different from what science means by biological age. Still, there is a real core to the idea, and it is useful.
Below you will read what biological age is and is not, which measurements matter, and what you can do with it as a man.
What is biological age?
Biological age is an estimate of how worn or fit your body is, rather than how many birthdays you have had. Where your calendar age rises by exactly one each year, your biological age can run faster or slower, depending on your lifestyle, genes and health.
The idea is simple: not everyone ages at the same pace. Someone who smokes, moves little and sleeps badly ages on average faster than someone of the same age who does not. Biological age tries to capture that difference in a number.
Important: there is no single official, validated "biological age" that your GP measures as standard. It remains an estimate, built up from several signals.
What is the difference with metabolic age?
Metabolic age is something else, and often less reliable. It is usually a number that a scale or fitness app calculates from your resting metabolism and body composition. It sounds scientific, but the calculation differs per device and is rarely validated.
So see metabolic age mainly as a rough indication, not a medical measurement. If your lean muscle mass rises, the number can fall, which can be motivating. But do not hang hard conclusions on it.
Biological age in the scientific sense goes a step further and looks at things that really relate to ageing, as below.
How do you measure biological age reliably?
The most reliable measures are not a single blood test, but functional measurements and DNA patterns. Walking speed and grip strength, for example, predict surprisingly well how your older years will go. So-called epigenetic clocks read chemical marks on your DNA. The table below lists the main ones.
| Measure | What it measures | How reliable |
|---|---|---|
| Epigenetic clock (DNA methylation) | chemical marks on your DNA | Scientifically strong, not yet standard care |
| Walking speed | how fast you walk a stretch | Good predictor of survival in older adults |
| Grip strength | strength of your hand grip | Strong predictor, stronger than blood pressure |
| Online "age test" (free) | usually a questionnaire | Variable, often not validated |
In a large analysis, walking speed clearly related to survival: in men aged 75, predicted ten-year survival ranged from about 19 percent in the slowest walkers to 87 percent in the fastest (Studenski et al., 2011). Grip strength is an equally strong signal (Leong et al., 2015).
Are those online biological age tests accurate?
Usually only partly. Many free online tests are a questionnaire about your lifestyle, and those give a rough impression, not a precise measurement. An epigenetic clock from a lab is more accurate, but you do not buy that for a few euros and it is not yet in standard care.
That does not mean they are worthless. An honest lifestyle test can get you thinking about smoking, movement and sleep. As long as you see the number as a mirror and not a diagnosis, there is little wrong with it.
What I would avoid: paying for a "biological age" based on a single blood value alone. One marker is simply not a clock.
Which blood values say something about ageing?
No single blood value measures your biological age, but a few values do give a picture of how your body is doing. Think of your long-term blood sugar (HbA1c), your cholesterol and inflammation values. Together they sketch risk, not age.
The Dutch health institute RIVM points out that many of these risk factors run silently: you do not feel them, but they do move with your lifestyle. That is why a baseline measurement can be useful as a comparison point for later.
If you want to measure several of those values at once, an extended health check can be a logical starting point. Every result is assessed by a BIG-registered doctor.
What can you do to stay younger on the inside?
The dials that favourably influence your biological age are the familiar ones: moving, building strength, not smoking, being moderate with alcohol and sleeping enough. Dull, but it works, and the effect is bigger than any supplement hype.
Strength is extra worthwhile for men, because muscle loss speeds up after fifty. How to counter that is in sarcopenia and muscle loss. And the broader picture of healthy ageing is in our guide to healthy ageing for men.
Want to know what lifestyle really does for your life expectancy? We cover that in living longer as a man. Start small, and see a test result as a starting point, not a final verdict.
Sources
- Horvath S. DNA methylation age of human tissues and cell types. Genome Biol. 2013;14(10):R115. PMID 24138928.
- Studenski S, Perera S, Patel K, et al. Gait speed and survival in older adults. JAMA. 2011;305(1):50-58. PMID 21205966.
- Leong DP, Teo KK, Rangarajan S, et al. Prognostic value of grip strength: findings from the Prospective Urban Rural Epidemiology (PURE) study. Lancet. 2015;386(9990):266-273. PMID 25982160.
- RIVM. Risk factors for cardiovascular disease. Available via rivm.nl.
Every blood test result at Caliber Health includes a professional assessment by a BIG-registered doctor. For treatment decisions, discuss your results with your GP.
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