How old are you really? This calculator can tell you.

By Cathy Johnson.

Sure, you know how many birthdays you’ve clocked up. But how old are you on the inside? A new calculator reveals this, giving you a different age that’s arguably a lot more meaningful.

We’ve all heard that 40 is the new 30. Or depending on your age, you might prefer ‘50 is the new 30′, or ’70 is the new 50′.

It turns out there can be some truth to this. But you could also be 30 – and more like 50. And we’re not just talking about your choice of clothing or hairstyle.

While you have no say in your chronological age – the number of years you've clocked up since birth – your biological age is something different altogether. It reflects how healthy your insides are, and this can bear little resemblance to the age on your last birthday card.

Professor Ulrik Wisloff prefers the term 'fitness age' because it turns out one thing that says a lot about the health of your body's tissues is your fitness level.

By comparing your individual fitness level with the average fitness level of others the same age, you can get a measure of your personal fitness age.

Calculating your fitness age.

Wisloff, director of the KG Jebsen Centre for Exercise in Medicine at Norwegian University of Science and Technology, and his team have developed an online calculator to help you figure out your personal fitness age, and you don't have to go anywhere near an exercise bike or treadmill (you might need a tape measure though).

Relying on a few simple questions like your age, your gender, your height, waist size and exercise regime, it's been used by more than three million people so far.

If your fitness is lower than average for your age, then your fitness age is older than your actual age.

But conversely, if you're fitter than usual, it's like you've turned back the clock, with more years ahead of you.

A 50-year-old for example could conceivably have a fitness age between 20 and 75 – depending mainly on the intensity and frequency of their physical activity, plus other measures entered into the fitness calculator.

It's for real.

Working out your fitness age isn't just a trivial game, says Wisloff, who for the past year has been in Australia, collaborating with researchers at the University of Queensland.

Your fitness age has been shown in a scientific study to be a meaningful guide to how many years of life you've got left. It's not set in stone of course, but rather an estimate, based on statistical likelihood. In fact fitness might be a stronger predictor than traditional risk factors used to estimate life expectancy – like being overweight, having high blood cholesterol, high blood pressure and smoking. (Wisloff and his team are soon to publish their research on this notion.)

"It's not just an algorithm that is for fun," Wisloff says. "It's based on 60,000 people's lives over 27 years. It's for real and it's so easy to use.

"Every GP or health professional all over the world can use it as a first line risk assessment without taking a blood sample or measuring blood pressure. You can do it at home."

How does fitness help you 'get younger'?

Exercise has a long list of health benefits that could feasibly help you live longer. But Wisloff thinks the bottom line as to why fitness is such a strong predictor of life span is that it trains your heart to pump more oxygen-rich blood around your body.

"Several studies have shown if the heart pumps more blood, the muscles are able to receive and utilise that for work. The oxygen maximises cell function. The reason we are living on the planet is because oxygen became available. I think that's basically the secret. Every single cell needs oxygen."

Lowering fitness age.

Having grasped the wonderful (or sobering) fact your fitness age is actually saying something pretty important, what can you do about it?

You can lower your fitness age simply by doing more exercise. But to maximise the effect, it's important to include some high intensity exercise.

Wisloff and his team have developed a regime that can help you lower your fitness age significantly in seven weeks. (Exactly how much you can lower it will vary from person to person, but the advice is based on the best scientific knowledge about what will work.)

If you think exercising two to three times a week with bursts of fairly high intensity sounds too physically intense for you, Wisloff insists it's do-able. "We have done this with people with heart failure," he points out.

He says "pretty much everyone", bar those with unstable angina or serious heart rhythm problems, can do it. (If you want more guidance on whether you're up to it, there's a pre-exercise screening tool that might help.)

"Our regime is not really hard because we suggest working at an intensity that is 20 beats per minute below your maximum." This is not as hard as some high intensity exercise programs that have had media attention and which require your muscles to work anaerobically (without oxygen).

"You will not be totally exhausted when you finish [our program]. It's easier than people think."

Of course it does still require effort but the idea of turning back the clock is a powerful motivator, says Paul Taylor, a Melbourne-based health behaviour coach and developer of a less well-validated biological age calculator used in early series of The Biggest Loser TV show. "Getting younger, you know, everyone wants to get younger," Taylor says. "A calculator that tells you you're 15 or 20 years older than you thought gives you a real slap between the eyes."

How the calculator works.

Traditionally, determining an individual's fitness accurately has been tricky. It's involved elaborate tests to measure your VO2 max - how well your body takes in and uses oxygen.

A few years back though, Wisloff's team developed an earlier version of the fitness calculator after showing you could estimate someone's fitness pretty closely if you plugged certain parameters like waist circumference, heart rate and exercise habits into an algorithm.

But this was based on only 5000 people. The latest calculator includes some refinements after the team studied its accuracy for some 60,000 people aged 20 to 90.

A few things to note:

Some people might still die significantly earlier (or later) than their fitness age would suggest because of factors unrelated to fitness. But this is relatively rare.

The calculator does not ask if you smoke because, while smoking does reduce life expectancy, it's thought the influence is relatively small compared to fitness (but this is currently being tested).

The effects of things like stress and social isolation are also real but much further down the impact scale.

And what about time spent sitting? Wisloff can't comment until a related study he's involved with, which explores this issue, is published.

This post originally appeared on the ABC and was republished here with full permission. 

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