PETER WALKER: Are slim people ALWAYS fitter than fatties?

For the best part of 25 years I’ve been active – I walk or cycle most days, and in normal times my commute is a six-mile round-trip on my bike.

It wasn’t always this way. In my early 20s, I gave up a secure office job to become a cycle courier. I’d barely been on a bike for years, but it didn’t take long before I’d developed a bit more speed, then stamina.

After a while, in a turn of events that left me as surprised as anyone, my legs developed muscles. And soon afterwards I acquired that sort of virtuous glow only really seen among the very young and physically fit.

Mine might have been an extreme example but the health benefits of physical activity, incorporated into your everyday life are well known. 

A Danish study involving 30,000 people tracked over 15 years, found that those who cycled to and from work were 40 per cent less likely than others to die early.

Now 52, in my role as a political journalist, I still spend time running between meetings in Parliament – or at least I did before lockdown. But even before the pandemic, I seemed to spend more and more time at a desk.

For the best part of 25 years I’ve been active – I walk or cycle most days, and in normal times my commute is a six-mile round-trip on my bike, writes PETER WALKER. Pictured: Stock image

I am all too aware of the risks that sedentary behaviour could carry for my heart, brain, lungs and bones – among other bodily functions. 

But I still look in pretty good shape, so I wanted to know if my more relaxed regime was keeping me healthy and if it was counteracting all those hours in an office chair.

To find out just how fit I really was, I became a guinea pig, festooned with electronic gadgets that tracked my movement, the time I spent sitting down, heart rate and calories burned. 

HEALTH HACKS: Exercising in the cold burns more calories 

We have different types of fat cells in our bodies. 

Yellow fat cells store energy from food, while brown fat cells are better at releasing energy.

The more brown fat we have, the more energy we are able to burn when exercising and even when resting. 

And according to studies, the body lays down more brown fat cells in colder, winter months.

It’s believed this is because the body expends more energy in cold weather to keep warm (shivering, for instance). 

Theoretically, doing exercise in the cold triggers the body to create more brown fat, to help burn more energy when resting.

I also underwent a series of tests of my fitness and general physical health, and interviewed some of the world’s most renowned exercise experts to talk me through the numbers.

Some measurements were reassuring. For example, my resting heart rate is low, at about 48 beats a minutes, and I remained significantly fitter than average. But others were more worrying.

I borrowed a tiny stick-on activity tracker of the sort usually used in university research, wearing it 24 hours a day for weeks at a time. This was just before the pandemic struck, so it captured my (now almost forgotten) normal pattern of working.

Every single move I made was logged and fed into a website. While on weekends there were occasional periods of sitting, these were generally broken up by flashes of activity such as playing football in the park with my son.

Workdays were much more sedentary, despite my cycling commute. 

On my most busy days, from about 2pm to 6.30pm I was sitting down continuously, regularly clocking up nine hours or more of immobile time??.

On busy, active weekend days it could still easily reach five or six hours.

Is being sedentary all that harmful? Yes, according to research. 

One massive study tracking more than 120,000 people in the US found those who averaged six hours or more sitting per day had a higher risk of dying from all sorts of reasons, such as heart disease, strokes, cancer, diabetes, kidney disease and Alzheimer’s.

But regular activity can limit the damage. Even low-intensity exercise, such as standing up or walking around, triggers our muscles to release compounds that help turn fat and calories we eat into energy, rather than store them.

If someone stays sitting down, this doesn’t happen – the largest muscles, in the legs and back, go into a sort of ‘sleep’ state called downregulation. Ultimately this increases the risk of weight gain and associated health problems.

Another test I carried out was particularly unforgiving. Before lockdown I travelled to Roehampton University to meet exercise and diabetes expert Dr Richard Mackenzie.

There I did a ‘ramp test’, which involves pedalling on a stationary bike at ever-increasing speeds, while wearing a mask that measures how much oxygen you consume. It’s designed to measure the absolute limit of our fitness ability.

When the results came back my score was 40 – just between ‘good’ and ‘excellent’.

But I had done the same test a few years earlier and scored 53, which put me in the wonderfully named class of ‘superior’.

A Danish study involving 30,000 people tracked over 15 years, found that those who cycled to and from work were 40 per cent less likely than others to die early. Pictured: Stock image

What had changed? Back then, my bike commute was roughly twice as long and I did other activities, including swimming.

It was a wake-up call. But there was worse to come. At Roehampton University, Dr Mackenzie’s team also measured my body fat percentage, using a high-tech device called a BodPod.

You sit inside a booth and it uses blasts of air and a complicated algorithm to do the calculations.

For middle-aged men, a body fat percentage a few points above ten per cent is good, and anything up to 20 per cent is acceptable.

My score was 30 per cent. Not just overweight, but obese.

I was confused. I’m 5ft 9in, and around 10st 12lb, giving me a body mass index (BMI) score of about 22 – in the middle of healthy. My waist size is 31in, and has been for the past decade.

So where was all this fat?

One possibility was that the BodPod gave me a dodgy reading, which is unusual but does happen. There’s also a chance I’m carrying large amounts of visceral fat.

These are fat cells wrapped around internal organs such as the liver and stomach, increasing the risk of things like type 2 diabetes and fatty liver disease. But it’s rare for someone as active as me to have ‘hidden’ fat like this.

Puzzled, I contacted Robert Ross, a leading expert on weight and activity from Queen’s University, Canada, for his advice.

He didn’t seem worried in the least. Dr Ross is a firm believer that the best weight-based measure of health is waist size.

Dr Ross tells me anything under 37in, for men, is fine. For women, it’s under 31.5in. I ask him: should I just maybe worry a bit less? He replies: ‘Amen, Peter.’

The link between weight and fitness can be complicated in all sorts of ways, not least the idea of ‘fat and fit’. 

A Spanish study published last week suggested that physical activity alone isn’t enough to undo the negative effects of excess bodyweight on heart health.

But other research has shown that unfit, lean men are more at risk of death than men who are fit and obese.

For me, that alarming body fat reading remains a mystery. Without a full body MRI scan, I’ll never be sure.

The good news is that if I do have some visceral fat hiding inside, aerobic exercise is one of the very best ways to get rid of it, and the effects can start immediately. So with that, I’m off for a bike ride.

© Peter Walker, 2021

  • The Miracle Pill by Peter Walker (Simon & Schuster UK), £16.99.

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