I’m a short, round-faced person, so I’ve spent many years of my life trying to appear older than I am. But when the fitness tracker I’ve worn almost religiously for three years – Whoop – launched a “biological age” feature, I was, for the first time ever, smug about being mistaken for a teenager. 

Biological age refers to physiological features and health metrics, as opposed to chronological age. And the wellness world is obsessed: 52 per cent of people now believe they’ll be healthier in the next few years than they are now because they’re investing in longevity, according to Euromonitor International’s ‘Top Global Consumer Trends 2025’. Variations of a biological age score also now feature on tracking devices Garmin, Oura and Ultrahuman as demand for knowledge of our healthspan increases.  

My device measures my biological age based on nine measurements: sleep consistency, hours of sleep, time in heart rate zones 1-3 (moderate intensity), time in heart rate zones 4-5 (high intensity), strength activity time, steps per day, Vo2 Max (the maximum amount of oxygen your body can use during exercise), resting heart rate, and lean body mass. 

It claims to test all of these metrics against clinical guidelines and age standards to let you know how your body is ageing. At 29, I was thrilled to see that my biological age is under 18. 

While a fitness strap may not feel as high-tech as some clinical assessments you can get for longevity, they offer one big bonus when it comes to testing ageing: continuous data. ‘Periodic clinical assessments can offer real precision for health insights,’ says Dr Max Gowland, a biochemist specialising in longevity, founder of healthy ageing supplement brand Prime Fifty, and chief scientific officer at FutureYou Cambridge. ‘But the key is consistency: by tracking patterns over time, you can identify whether your biology is ageing faster or slower than expected, even if the device itself does not directly accurately measure biological age,’ says. 

As for setting goals when it comes to biological age? ‘For some, achieving a biological age 10–15 years younger than their actual age is possible, but it’s not necessary for everyone. Biological age is best viewed as a dynamic marker of health trajectory, not a competition. The emphasis should be on personalised optimisation, rather than an arbitrary decade offset, since genetics, lifestyle, and prior health all influence the achievable range,’ he says. 

As marathon runner and a strength coach with a biological age much younger than my years, here are my steps for adding ten years to your “biological” life.

Strength training

Guidelines recommend two to four weight-bearing workouts a week to protect our muscular, bone, and heart health. Hit or exceed those targets on Whoop, and your age will maintain or reverse. Do fewer, and your biological age will increase. 

My tracker defines any resistance-based workout as a strength activity, from weightlifting to Pilates and yoga. It tells me my recent average is two and a half hours of strength-based work a week. Recently, I’ve been splitting that across two or three full-body gym workouts a week – well within the NHS recommendations for everyone between the ages of 19-64. This routine alone has been enough to wipe 1.6 years off my life. 

I’ve been lifting weights for over 10 years and coach strength classes, so I have advice for those who struggle to reap the benefits: no matter your age, strength training should feel difficult, and it doesn’t have to be intimidating. I know they sound juxtaposed, so let me explain. On the former: your muscles strengthen when they are pushed close to failure, meaning you do need to struggle to complete at least some of the exercises in your workout. 

However, hard doesn’t have to mean horrible. Whether it’s a barre class that makes you pulse until your arms shake or a gym session where you strain to lift a barbell just once, there are so many ways to build strength – the only difference is you might prefer one and keep coming back for more.

Cardio 

I historically hated cardio, but over the past three years, it’s become my go-to workout. For me, it’s running – especially for getting outside socially in summer and training for big goals like marathons. The sport isn’t for everyone, and cycling, zumba, trampolining or anything else that gets your heart rate up counts too. 

My device reads cardio output in heart rate zones. There are five zones, starting at zone 1 (any activity that increases your heart rate to 40-50 per cent of your maximum) through to zone 5 (90-100 per cent of your max). 

Zones 1-3 generally increase endurance and capacity for overall health; Zones 4-5 typically increase the strength of the heart and help your body adapt to demand. Because higher zone work is more taxing on the body, you need less of it for similar results. PT Nancy Best, founder of Ladies Who Crunch, also says excess time in higher zones can be counterintuitive: ‘We have stressful lives that put a lot of stimulation on our bodies. Exercise is an additional stress, which is good, but too much can lead to recurrent injury, issues with sleep disruption and general fatigue.’

Chloe Gray used to hate running but has since completed a marathon (Photo: Matthew Bowen)

On average, I spend just under four hours a week in zone 1-3. That sounds like a lot, but the majority of work in that heart rate zone is achieved via both training and incidental walking. I also spend an hour and a half in zone 4-5, which exceeds the government’s recommendation for 75 minutes of vigorous activity a week. That’s because I was running for a speed goal – now I’m about to start training for another 26.2 miler, which will decrease as long, slow runs take centre stage and interval work takes a back seat. 

All of this cardio and strength combine to give me a very low resting heart rate, indicating my heart is strong enough to pump a lot of blood around my body with every beat, and knocking 2.2 years off of my life. It also improves my Vo2Max, which my tracker tells me is 52, putting me in the top 5 per cent of people for my age and biological sex. That takes nearly four years off my age.

Steps 

When it comes to steps, more is not always better, with research published in The Lancet finding that health benefits plateau at around 7,500. Yet, I hit an average of double this, coming in around 15,000-16,000 per day. 

That’s rarely a health-focused decision for me. Instead, it’s a natural side effect of living in a city, a 20-minute walk away from a tube and a supermarket, with a busy work and social schedule and no car. I know most people can’t walk that far every day: it’s time-consuming, and research always shows the biggest benefits always come from doing slightly more than you currently do, whether that’s increasing from 3,000 to 5,000 or heading into five-digit figures. But walking has the perk of being low-impact, requiring little skill and supporting your mental health, so if you can turn your commute into a stroll, I recommend it. 

Sleep 

I don’t enjoy bragging about good sleep because I know how hard it is to cope when you’re not getting it. I’m a naturally awful snoozer, so I have become somewhat fanatic about my shut-eye. Every night, I wear earplugs, an industrial-looking Drowsy eye mask and mouth tape, while also popping magnesium tablets to lull me into a deep sleep. 

Yet, my scores here are only average by Whoop’s standards, though I’m aware that it may be good by other people’s: I average 7.38 hours of sleep a night, which falls below my average sleep need of 8:26 though still means I’m significantly boosting my health. When it comes to sleep consistency, meaning how similar your bed and wake times are, a key component of circadian rhythm, which drives hormonal health, metabolism and immunity, I’m also OK: I average 78 per cent, while the tracker recommends 90 per cent for optimum health and 80 per cent “to get by”. 

Given that these readings aren’t perfect, yet still manage to knock a collective 1.6 years off my age, I’d say worrying about sleep is a fallacy. 

Other health habits for longevity

Even though I’ve just shared all of my stats, I feel the need to disclaim: what I can do in 24 hours is very different from what others can do. Spending hours with a raised heart rate from walking, running and the gym is a privilege that comes from being young, with no caretaking responsibilities, a flexible work schedule and a job in the health and fitness industry. But it may also be useful to know that my health is not perfect and my habits sometimes, on the surface, seem to go against my goal of maintaining good health. 

I eat mostly whole foods, but I have some dessert or processed foods every day. That includes chocolate, shop-bought bread and bagels and, on long run days, sugary sweets. When you move a lot, opting for a diet of exclusively low-calorie or ‘healthy’ foods is actually counterintuitive: you can’t eat well if you’re not eating enough. My exercise routine and fitness levels would drop dramatically if I over-stressed about my nutrition or aesthetics. 

I drink alcohol too – but normally no more than a couple of times a week, and never alone. I’m not one to turn down a couple of wines mid-week with friends or a Saturday night out that’s later than I’d like recorded on my device. Afterwards, I’ll be alerted about my bad night’s sleep or alarming physiological response to booze – but one thing Whoop can’t track is social connection. 

Community and friendship are potentially the biggest extenders of life – and not something that should be neglected in longevity science in favour of more measurable science. One of the longest studies ever carried out, the Harvard Study of Adult Development, which began in 1938, found that positive relationships help to delay mental and physical decline and are better predictors of longevity than social class, IQ and even genes. I’m not saying alcohol has to be included in socialising, but that, sometimes, you’re better off staying up late with your mate than stressing about hitting your optimal bedtime routine. 

I have no rules for my wellness, just a decade of working out what feels good to me. And, to summarise, that’s: walking as much as possible, exercising regularly in a way I enjoy, sleeping as well as I can, and never sacrificing friendship in the hunt for perfect health.