Biological age and why it matters

You all know how old you are, right? That’s your calendar age! But do you know your biological age? Unlike your calendar age – a mark of the time elapsed since you were born, your biological age is a measure of your true body age. Let me explain a little more!

Your body ages at a certain rate, depending on a number of factors (we’ll come to that a bit later). This could be at a lower or higher rate than your calendar age. And we all age at different rates! Have you ever looked at someone who’s 50 and thought…wow don’t they look like they’ve just turned 35! Or have you met a friend you haven’t seen for ages and thought, gosh they look like life put an extra 10 years on them! Why am I telling you all of this? Well, because unlike calendar age which you can’t control, you can change your biological age and slow down the rate of ageing. This means having the possibility of living more years while being fit and healthy. That’s exciting, right? Want to know more? Read on….

What does biological age actually mean?

Biological age, also called functional or physiological age, is often described as your true body age or a measure of your biological ageing progress. Compared to calendar age, biological age is a better predictor of longevity (or how long you’ll live for), as well as your healthspan or the estimated length of time of your life spent being in good health and free from long-term diseases related to ageing (1).

The biological age of people with the same calendar age of 38 can vary from 28 to 61!

Knowing your biological age means knowing the rate at which you’re ageing. A group of researchers wanted to find out if people start to age at different rates even before they reach their midlife point (2). They studied almost 1000 young adults and followed them from birth until the age of 38. The researchers determined the biological age of the participants based on how well their bodies were working. They looked at their mental function, as well as study the health of the different organs and systems like the heart, lungs, liver, kidney and immune system. What they found was astounding! The biological age of people with the same calendar age of 38 varied from 28 to 61. This means that for two people of the same age of 38, one is functioning as well as someone in their late 20s, whilst the other is functioning more like someone in their sixties. Who would’ve thought there could be such a stark difference between your calendar and your biological age! Most importantly, by knowing the factors that influence your biological age, you can work on these to knock off some years of your functional age. More on this later.

How is biological age measured?

There are a number of ways researchers can measure biological age. A popular method, reputable labs around the globe use, exploits epigenetic data to measure what’s called DNA methylation. I know I’ve just given you lots of information but hang in there, I’ll explain! We store information in our body in two forms: the genome and the epigenome. Your genome is made up of your complete DNA which holds your unique genetic code. It’s often likened to a recipe book, which has instructions to make all the proteins that your body needs. Your epigenome is made up of all the chemical compounds and proteins which can attach to the DNA. It controls the way genetic information is packaged and read by the cell. It doesn’t affect the sequence of your DNA but it determines which genes are switched on or switched off. Going back to DNA methylation, this is a common type of epigenetic modification. It involves chemical additions to the DNA which accumulate over time and is a good marker for ageing. Essentially, the clock of ageing can be measured by tracking the methylation of DNA. 

Biological age can be determined by measuring DNA methylation or telomers length

Another way of working out biological age is telomeres length. Telomeres are the protective caps found at both ends of each chromosome. They have an important role in preserving information in the genome by protecting chromosomes from sticking together and degrading. Telomeres shorten each time a cell divides and they shorten progressively as you get older. When telomeres become too short, the cells enter a state called senescence, when they’re no longer able to divide.  They’re often called ‘zombie cells’. These cells are linked to inflammation and age-related diseases.  So, measuring telomere length can also be a good indicator for the ageing process.

How can you test your biological age?

A number of at-home test kits are currently commercially available. These are usually based on either testing a saliva or a blood sample to give an indication of your overall biological age.

Elysium Health – a US-based company- have developed a home test called Index. The test costs $499 but subscribers of the company’s supplement Basis can get the Index biological age test for the reduced price of $299. Life Length, myDNAage are other companies from which you can buy at-home test kits.

Can you tell someone’s biological age?

As subjective as this can be, the short answer is possibly yes! A number of studies have shown that the subjective assessment of age, from photographs for example, correlates well with measured biological age (2) (3). In a study, undergraduate students at a university in the US were shown photos of participants without any additional information (2). The students rated participants with higher biological age as looking older than their biologically younger peers. So, in the absence of any testing, you may be able to guess your biological age, possibly by knowing how old you look!

Can you turn back time?

As well as genetics, your biological age is influenced by a number of elements, including diet, exercise and other lifestyle factors like smoking, alcohol, stress and sleep. If you or other people think you look older than you actually are -or if by any chance you’ve tested your biological age and it’s higher than your calendar age- don’t despair! There are plenty of things you can do reduce your biological age and increase your healthspan.

Essentially, it’s things you already know about! Mainly, a healthy diet, exercising regularly, not smoking, drinking in moderation, lowering stress and getting enough good quality sleep. What’s exciting is there could be other strategies which could have a significant effect on longevity. We don’t specifically know the ideal factors, as this field is fairly new, but we know that in animals, things like fasting and calorie restrictions can increase longevity. I’ll talk about this in more detail in a separate blog post.

As it turns out, age could be just a number! Knowing your biological age could help you determine your rate of ageing, and this means you can take active steps to help you age in the right direction!


1. Examination of the Dimensions of Biological Age. Jazwinski, S. Michal and Kim, Sangkyu. 2019, Frontiers in Genetics, p. 10: 263.

2. Quantification of biological aging in young adults. Belsky, D W, et al. 2015, PNAS, pp. 112 (30) E4104-E4110.

3. Perceived age as clinically useful biomarker of ageing: cohort study. Christensen, K, et al. 2009, The British Medical Journal, p. 339:b5262.

6 Comments Add yours

  1. Great article, I really enjoyed it, spot on information. I’m also a biohacking my body, with nrf2, nrf1, Nad as my company has 31 peer reviewed studies. Would love to talk with you further. Thanks so much


    1. Thanks Karen for the feedback. I’ll make sure I look at the studies.


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