Your body is not a number so should we really care about our biological age?

There is something rather exhausting about being a woman in midlife. Just when you think you have made peace with one set of numbers, somebody produces another. Weight. BMI. Waist measurement. Blood sugar. Cholesterol. Steps. Calories. And now, apparently, biological age.

I came across mine on the Boditrax machine at the gym. I had half expected it to announce that I was about 100 and suggest I go home for a lie-down. Instead, it gave me the usual collection of body-composition figures, including muscle percentage, alongside another estimate of what was going on beneath the surface.

I knew these figures were estimates rather than an infallible medical verdict, but I found them fascinating. Month after month, I could see patterns. When I exercised regularly, things changed. When I altered the kind of training I was doing, they changed again. Once I started doing more strength work, my muscle percentage began to climb.

I loved seeing that. There is an undeniable satisfaction in being presented with evidence that the squats and weights might be doing something. I was rather less enthusiastic about climbing onto Boditrax during periods when my diet had gone off piste.

But there was a problem, my BMI barely moved. My weight did not fall as I became stronger. Sometimes it went up, even while my muscle percentage was moving in what looked like the right direction. So which number was I supposed to believe? And why, after all these years, did I still want one of them to tell me I was doing well?

My relationship with scales goes back much further than Boditrax. When I worked at The Journal in Newcastle, a group of us used to walk to Grainger Market at lunchtime for weigh day. There was a machine there where, for 20p, you could step onto the scales and receive a little ticket with your weight printed on it.

I kept mine. I stapled those tiny tickets into my diary so I could watch the numbers rise and fall. There were no graphs of muscle mass or metabolic-age calculations, no smartwatches back in the day. There was just a number printed on a scrap of paper.

At some point, though, that number stopped being information and became instruction. I stopped eating lunch before I weighed myself because I was frightened it might make me heavier. I thought about what clothes I was wearing. I chose lighter ones some days. I removed a layer before stepping onto the scales. All that effort to persuade a machine in Grainger Market to print a slightly smaller number on a 20p ticket.

I can see this was ridiculous now. I wasn’t measuring my health, I was just changing my behaviour to please the measurement. That memory came back when I started thinking about biological age. The technology has changed beyond recognition since those lunchtime weigh-ins, but I wonder whether women have.

We have spent decades being handed numbers and told, explicitly or otherwise, that smaller is preferable. Weight, dress size, waist measurement, calories. Then midlife arrives and adds a fresh layer of complication because our bodies are changing at the point we are being offered more sophisticated ways to measure them. Hormones shift. Sleep can become erratic. Recovery feels different. Muscle becomes more important. The body I have now is not the body I had at 30, nor should I expect it to be. Ageing is not evidence of poor performance.

Chronological age is the number of birthdays you have had. Biological age is an attempt to estimate how the body is functioning as it ages. There is no single standard clinical test. Different systems use different information, which might include fitness, body composition, metabolic health or blood markers. Research can go much further, looking at biological markers such as DNA methylation.

That makes biological age interesting, but it does not make the number handed to you by a gym machine a definitive judgement on how well you are ageing.

If a measurement encourages me to pay attention to my health, build muscle or notice changes over time, useful. If it becomes another score by which I decide whether my body is acceptable, we have merely found a more technologically impressive way to repeat an old mistake. I do not want a gold star for being biologically younger than I am. I would quite like to be healthy at the age I actually am.

BMI is a good example of what happens when a useful measurement is asked to do rather more than it was designed for. It is a straightforward screening tool based on height and weight. It does not directly measure muscle, body composition, fat distribution, fitness or metabolic health. Two people can share the same BMI while having quite different bodies and different health risks.

Jordan Chadwick, director at Tonic, says that is why BMI needs context.

“BMI can still be useful as a quick screening tool, but the problem comes when people treat it as a complete verdict on their health. It was never designed to explain the full picture, and on its own it can miss some of the most important details.

“Two people can have the same BMI and be in very different places health-wise. One person may have more muscle, better fitness and stable blood sugar, while another may be carrying more weight around the waist and have a higher level of metabolic risk. That is why looking only at height and weight can be too blunt.”

Jordan Chadwick, director at
Tonic.

This does not mean weight suddenly doesn’t matter. Nor does it mean we should ignore established health risks because we prefer another measurement. It just means one figure can’t tell the whole story.

These days I am interested in if I can lift something heavy, or walk for an hour. Can I carry the shopping without feeling as though I am undertaking an endurance event. Can I dance, or get off the floor without making the sort of noise my mum’s knees used to make? Can I keep up with Cyrus?

None of this produces an impressive printout, it just tells me something about the body I am living in.

I wish we talked more to women in their 40s and 50s about strength without immediately wrapping the conversation in weight loss. Muscle matters as we age because it supports strength, mobility and physical function and that has changed the reason I train.

I love the gym. I love Zumba and combat-style classes and realising I can now do something that once left me wondering whether I had made a terrible mistake. But I no longer want exercise to be penance for lunch, I just want to be strong.

There is something satisfying about lifting a weight that once felt impossible. Nobody needs photographic evidence of me doing it, and I have no desire to turn my workouts into an inspirational montage these days. I like what strength gives me outside the gym.

It also makes the bathroom scales considerably less interesting so they’re currently gathering dust. I believe a body can become stronger without becoming smaller. It can gain muscle without delivering the dramatic weight loss we have been trained to applaud. For women of my generation, that can take quite a bit of unlearning.

Movement matters, of course, but I am suspicious of any wellbeing advice that means women have to reorganise their entire existence around being healthy. A gym session counts, but so does walking. Taking the stairs counts, getting away from a desk also counts, and even dancing in the kitchen while cooking counts.

I happen to enjoy exercise, but even I have work, family, tiredness, hormones and the general admin burden of being a functioning adult to contend with. There are weeks when everything slots beautifully into place and others when it very much does not.

The exercise we continue doing is more useful than the theoretically perfect programme we abandon after three weeks because it takes a lot of logistical planning. Midlife women do not need another regime at which to fail.

Blood sugar, cardiovascular health and sleep do not make for terribly exciting wellness copy, but they do matter rather more than most of the fashionable shortcuts sold to us. Blood-sugar regulation forms part of the wider metabolic-health picture, and research has explored links between glucose regulation and markers associated with biological ageing. That does not mean a single glucose reading can reveal the secret age of your body.

The useful advice is to eat in a way that supports your health, move regularly, maintain muscle and pay attention when your body tells you something has changed. Rather annoyingly, there is no magic ingredient hiding at the back of the kitchen cupboard.

Then there is sleep. When I am tired, everything takes more effort. Cooking something decent feels harder. Exercise feels harder and my patience becomes less impressive. Resisting yet another coffee at the gym becomes a battle I have little interest in winning.

“Get more sleep” is also irritating advice for a woman in midlife when hormones may have other plans. It can sound like telling somebody caught in the rain that the solution is to just stay dry. The sensible aim is not perfect sleep, perfect food, perfect exercise and a collection of immaculate health scores. It is to give the body a reasonable chance to just do its job.

This is where I remain conflicted about biological age. I like data. I enjoy seeing my muscle percentage increase. I find it reassuring when something measurable confirms that the work I am putting in has made a difference. I also remember those little tickets from Grainger Market.

The scale goes up. My watch tells me I slept badly. Boditrax produces another set of figures. It would be very easy to spend a huge amount of time monitoring a body I am supposed to be busy living in. And women are already very good at turning information into judgement.

A heavier body is not evidence of laziness and a missed workout is not a character flaw. A larger waist does not make somebody a failure. Nor should reaching 50 provoke an urgent attempt to convince a machine that we are really 42, because getting older is not a personal failing.

If knowing your biological age encourages you to look after your heart, maintain muscle, move more or take your health seriously, it has done something useful. If it makes you frightened of food, obsessed with scores or desperate to prove that your body is younger than the date on your birth certificate, I am not sure it has.

The question I keep returning to is not, How young does my body look? It is, How well is my body supporting the life I want to live?

I want to be strong enough to carry the shopping. I want to dance. I want to keep up with Cyrus when he is running around the park and I want enough energy to enjoy the life I have rather than spending it endlessly preparing my body for some supposedly improved version of that life.

And I would quite like the mental freedom not to regard every wobble, missed workout or unflattering measurement as a personal failure. Paying attention to our bodies matters, but there is a difference between caring for a body and spending your life trying to correct it.

I still use Boditrax and look at the figures. And yes, I still feel pleased when my muscle percentage moves in the direction I want. I am not going to pretend that several decades of conditioning disappeared because I wrote an article about it.

What has changed is the amount of authority I give the number. I am more interested now in whether I am getting stronger, whether I move regularly, whether I am eating reasonably well, whether I am getting enough rest and, crucially, whether exercise still adds something to my life rather than becoming punishment for living it. Those questions are harder to reduce to a neat score.

My body has carried pregnancy, given birth. It has exercised, danced, lifted weights, slept badly, recovered, changed and aged. It has got me this far. I do not need my body to convince a machine that it is younger than 50. I need it to carry me through what comes next.

Is it strength, better health markers, more energy, keeping up with your children or grandchildren, or feeling more at home in your own skin? And if somebody could give you a definitive biological age tomorrow, would you really want to know?

Occasional stories, experiments, discoveries and questions from Saffron & Cyrus.