Partly, yes. Your genes can’t give you a single “biological age” number, because your DNA doesn’t change as you get older. What it can show is whether you’ve inherited a tendency to age faster or slower at a cellular level. One of the clearest examples is TERC, a gene linked to the length of your telomeres: the protective caps on your chromosomes that shorten as you age. That tells you where to focus your efforts.
If you see your health as a long-term investment and want more good years, not just more years, knowing how your cells are likely to age is a useful place to start.
What's the difference between chronological and biological age?
Your chronological age is simple: it's how many birthdays you've had. Your biological age however, is how old your body behaves, based on how well your cells, organs and systems are holding up.
Two 45-year-olds can look and feel very different. One might have the heart health, muscle strength and energy of someone a decade younger; the other might not. That gap is down to biological age, and it's shaped by a mix of genetics and day-to-day lifestyle.
What's the difference between lifespan and healthspan?
Lifespan is how long you live. Healthspan is how long you live in good health, free from the chronic illnesses that tend to arrive later in life.
The gap between the two is growing. A 2024 study of 183 countries found that, worldwide, people now spend an average of 9.6 years of their life in poor health, and that this gap has widened over the past two decades (Garmany and Terzic, 2024). Closer to home, the latest ONS figures show that people in the UK can expect around 61 years in good health, the lowest level since records began.
For most longevity seekers, healthspan is the real goal. Biological age is one way of measuring whether you're on track.
What are telomeres, and why do they matter for ageing?
Telomeres are stretches of DNA at the very ends of your chromosomes. A common way to picture them is like the plastic tips on shoelaces: they stop the important genetic information inside from fraying.
Every time a cell divides, its telomeres get a little shorter. Eventually they become too short, and the cell stops dividing or dies. Over time, this build-up of worn-out cells is thought to contribute to the ageing of tissues and organs.
That's why telomere length is often used as a marker of biological ageing. In a study of people aged 60 and over, those with shorter telomeres in their blood had poorer survival, including a roughly three times higher death rate from heart disease (Cawthorn et al., 2003).
What is TERC, and how does it affect telomere length?
TERC is a gene that provides part of the instructions for telomerase, the enzyme that helps rebuild and maintain telomeres.
Small, common differences near the TERC gene affect how long your telomeres tend to be. In a large genetic study, each copy of one TERC-linked variant was associated with shorter telomeres, equivalent to around 3.6 years of age-related telomere loss (Codd et al., 2010). A later study of more than 37,000 people confirmed TERC as one of several genes that influence telomere length, and found that gene variants linked to shorter telomeres were associated with a higher risk of coronary artery disease (Codd et al., 2013).
In our Telomere-linked ageing (TERC) report, we look at whether you carry variants associated with shorter telomere length, which reflects faster telomere shortening.
How common are "faster-ageing" TERC results?
Across FitnessGenes members with a TERC result, around 47% have variants linked to average telomere length. Around 41% fall into a moderate-priority group, and about 11% carry variants placing them in the high-priority group for telomere-linked ageing.
In other words, more than half of members have at least some genetic tendency towards shorter telomeres, which is exactly why it's worth knowing your own result.
Is it a good thing to have longer telomeres?
Mostly, but it's not quite that simple. Research using genetic data suggests that longer telomeres are linked to a lower risk of heart disease, but may slightly raise the risk of some cancers, because cells that can keep dividing for longer can also be more likely to grow out of control (Haycock et al., 2017).
That's one reason we don't treat telomere length as a score to maximise. It's one piece of the ageing picture, best looked at alongside your other results.
Can you change your telomere length?
Your TERC genes won't change, but your lifestyle still matters.
In a study of over 2,400 twins, the most physically active people had telomeres around 200 building blocks longer than the least active, even after accounting for age, weight and smoking (Cherkas et al., 2008). Smoking and obesity, by contrast, are known to speed up telomere shortening: one study of over 1,100 women found each pack-year smoked was equivalent to extra telomere loss (Valdes et al., 2005). And in a small five-year pilot study, men who made comprehensive lifestyle changes to their diet, activity, stress management and social support saw their telomere length increase, while it fell in the comparison group (Ornish et al., 2013). Though larger trials are still needed to confirm that finding.
The practical takeaway is reassuring: the habits that support a longer healthspan, like moving regularly, not smoking, eating well and managing stress, are the same ones linked to healthier telomeres.
How does your TERC result fit with biological age testing?
Your TERC result tells you about your inherited tendencies, not your current state. To get the full picture, it helps to combine two types of test:
- A DNA (genotype) test shows the things you’re born with, such as whether your TERC variants put you at risk of faster telomere shortening. Your genes don’t change, so you only need to do it once.
- Biological age tests measure things that change over time, such as epigenetic clocks, blood markers and fitness measures like VO2 max and grip strength. You can repeat them to track your progress.
Your DNA explains why certain areas need attention, and ongoing tests show whether the changes you’re making are working.
How does FitnessGenes use TERC in your longevity plan?
Your TERC result sits in our Biological Ageing category, alongside genes such as FOXO3, which is linked to exceptional longevity, and TP53, which helps repair damaged DNA.
BASIL, our longevity platform, brings these results together with your lifestyle and health data. Rather than leaving you with a long list of genes, it ranks the daily actions most likely to support your long-term health, so you know what to prioritise first.
Get your DNA test here.
FAQs
Can a DNA test tell me exactly how old my body is?
No. Your DNA sequence doesn't change with age, so it can't give you a biological age number. It can show whether you're genetically inclined to age faster in certain ways, such as through shorter telomeres.
What does TERC stand for?
Telomerase RNA component. It's part of telomerase, the enzyme that helps maintain the protective ends of your chromosomes.
If I have a “high priority” TERC result, will I die younger?
Not necessarily. Genetics accounts for a relatively small share of how long we live. A high-priority result is a sign to pay closer attention to habits that support healthy ageing, not a prediction.
Can exercise really affect my telomeres?
Research suggests so. Studies have linked higher levels of physical activity with longer telomeres, though most of this evidence is observational rather than proof of cause and effect.
What's the difference between a DNA test and an epigenetic age test?
A DNA test reads your fixed genetic code. An epigenetic test measures chemical changes on your DNA that shift over time and with lifestyle, so it can be repeated to track progress.
Do telomere supplements work?
There isn't strong evidence that any supplement meaningfully lengthens telomeres in people. The best-supported approach is food-first, active, smoke-free living.
Is lifespan or health span more important?
For most people, healthspan. Living longer matters most when those extra years are spent feeling well and independent.
References
Cawthon, R.M., Smith, K.R., O'Brien, E., Sivatchenko, A. and Kerber, R.A. (2003) 'Association between telomere length in blood and mortality in people aged 60 years or older', The Lancet, 361(9355), pp. 393–395. Available at: https://doi.org/10.1016/S0140-6736(03)12384-7
Cherkas, L.F., Hunkin, J.L., Kato, B.S., Richards, J.B., et al. (2008) 'The association between physical activity in leisure time and leukocyte telomere length', Archives of Internal Medicine, 168(2), pp. 154–158. Available at: https://doi.org/10.1001/archinternmed.2007.39
Codd, V., Mangino, M., van der Harst, P., et al. (2010) 'Common variants near TERC are associated with mean telomere length', Nature Genetics, 42(3), pp. 197–199. Available at: https://doi.org/10.1038/ng.532
Codd, V., Nelson, C.P., Albrecht, E., Mangino, M., et al. (2013) 'Identification of seven loci affecting mean telomere length and their association with disease', Nature Genetics, 45(4), pp. 422–427. Available at: https://doi.org/10.1038/ng.2528
Garmany, A. and Terzic, A. (2024) 'Global healthspan-lifespan gaps among 183 World Health Organization member states', JAMA Network Open, 7(12), e2450241. Available at: https://doi.org/10.1001/jamanetworkopen.2024.50241
Haycock, P.C., Burgess, S., Nounu, A., et al. (2017) 'Association between telomere length and risk of cancer and non-neoplastic diseases: a Mendelian randomization study', JAMA Oncology, 3(5), pp. 636–651. Available at: https://doi.org/10.1001/jamaoncol.2016.5945
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Office for National Statistics (2026) Healthy life expectancy, UK: between 2011 to 2013 and 2022 to 2024. Available at: https://www.ons.gov.uk/peoplepopulationandcommunity/healthandsocialcare/healthandlifeexpectancies/bulletins/healthstatelifeexpectanciesuk/between2011to2013and2022to2024
Ornish, D., Lin, J., Chan, J.M., Epel, E., et al. (2013) 'Effect of comprehensive lifestyle changes on telomerase activity and telomere length in men with biopsy-proven low-risk prostate cancer: 5-year follow-up of a descriptive pilot study', The Lancet Oncology, 14(11), pp. 1112–1120. Available at: https://doi.org/10.1016/S1470-2045(13)70366-8