Michael Mosley is on the fast track to fitness

HIS 5:2 diet caused a stir worldwide. Can Michael Mosley do the same for exercise?

Michael Mosley says a few short, intensive bursts of exercise each week can bring dramatic benefits.

A YEAR ago I wrote a book that changed my life. A middle-aged medical journalist, I found myself the unlikely author of an international bestseller, The Fast Diet, and the recipient of a lot of grateful emails.

Now I'm hoping to do it again with Fast Exercise. Fast Exercise is based on a surprising and radical claim - that you can get fitter, healthier and better toned with just a few minutes of intense exercise a day, three days a week.

For those who missed it, the Fast Diet - often known as "the 5:2" - is based on the idea of intermittent fasting, also known as IF. Instead of aiming for slow, steady calorie restriction - the approach recommended by sensible dietitians that most people find impossible to stick to - with IF you slash your calories, but for only a couple of days a week (hence the catchphrase the 5:2). Although it may sound faddish, intermittent fasting is based on careful scientific studies (mainly animal, but some human) that suggest it not only leads to weight loss but has multiple other health benefits.

I was convinced enough by the science to make a documentary and then to write a book. I remember, shortly after we delivered the manuscript a year ago, pointing out to my co-author, Mimi Spencer, that there are about 50,000 diet books available online and the odds of us making an impact were, to say the least, slim. Mimi, who is an incurably optimistic Tigger to my Eeyore, was convinced we would succeed because our approach was offering not just a science-based diet but a modern take on an old tradition. Fasting, after all, has a long history. "It will be huge," she announced, as we sipped our calorie-free tea. She was right. As well as numerous doctors, politicians and a Nobel prizewinner, there have been endorsements from the likes of food writer Hugh Fearnley-Whittingstall and actor Benedict Cumberbatch.

One of the most striking things about the Fast Diet is how many men not only embrace it but are happy to tell the world they are doing it. I think it helps that "fasting" sounds challenging. It is also simple and straightforward, which again seems to appeal to men. Mimi's father is certainly a poster boy for this approach. Over the past few months he has lost more than 16kg and has had to buy new trousers. This is something I can identify with as I have lost 10kg, a few inches around my middle and found that most of my clothes no longer fit. I hate shopping but fortunately I have sons whose clothes I can now borrow (I haven't told them). I'm also wearing suits from 20 years ago that I never got around to throwing out.

Although I'm pleased with the weight loss, for me intermittent fasting was never about getting slimmer. Eighteen months ago I went to my GP with a suspicious mole and she suggested I have my blood tested. The mole turned out to be benign but the blood results were not. I had a fasting glucose of 7.3 mmol/l, which made me diabetic, and a "bad" cholesterol (LDL) of 5.5 mmol/l (the recommended level is less than 3). I shouldn't have been surprised because my father, who struggled with his weight all his life, died of complications from diabetes in his early 70s. I'd never felt the need to diet because I had never seen myself as overweight. Yes, I weighed in at 85kg, but when I looked in the mirror I saw someone slim, ageing well, almost athletic. This wasn't simply a case of middle-aged delusion; the surplus fat really was invisible. My fat wasn't sitting under my skin, bulging out in unseemly places. It was visceral fat, buried deep inside my body. I went for an MRI and saw not just the odd dab but litres of the stuff inside my abdomen, coating and clogging my internal organs. Visceral fat is particularly unhealthy because it is metabolically active, increasing your risk of diabetes and heart disease. It is surprisingly common, even in people of normal weight.

Rather than start on a conventional diet, I decided to try intermittent fasting. Unlike proper, hardcore fasting where you live for days or even weeks on few if any calories, IF involves a few days a week when you eat about a quarter of your normal calories. Being a television presenter with a taste for self-experimentation, I naturally made a documentary about my adventures. In the course of making Eat, Fast, Live Longer I came across different ways you can do intermittent fasting. The best-studied approach and the one that is likely to lead to the most rapid weight loss is ADF, alternate day fasting. As the name implies, you cut your calories every other day. I tried ADF but found it hard going and settled instead on a 5:2 pattern, cutting my calories two days a week. If you don't splurge on your non-fast days then this should lead to a weight loss of almost half a kilogram a week.

Dr Michelle Harvie and Professor Tony Howell of the Genesis Breast Cancer Prevention Centre, who have done proper clinical studies comparing two days a week of calorie restriction against a standard diet, found that those on the two-day diet lost nearly twice as much fat (about 4kg) as those on a standard diet, as well as seeing greater improvements in key biochemical markers such as insulin sensitivity. Intermittent fasting won't suit everyone, but it worked for me. Not only did I lose a lot of fat (10cm off my waist, 5cm off my neck) but I also saw huge improvements in my fasting glucose and cholesterol levels, both of which are now in the healthy range.

Yet even when I was doing IF I knew it was not enough. I realised that if I was going to maximise my chances of living into a healthy old age then I needed to do more exercise. The trouble is I hate running, jogging or going to the gym. Instead, I've taken up a very different approach, pioneered by (among others) Professor Jamie Timmons of Loughborough University. Jamie introduced me to HIT, high intensity training. Like IF, HIT is a radical solution to a modern problem, in this case how to get the most from a workout in the least possible time. HIT also eschews the "moderation in all things" approach. Instead of plodding away on a treadmill or cycling at a steady, sensible pace, with HIT you do a few extremely short bursts of exercise, intense enough to get your heart rate soaring, interspersed with a couple of minutes of recovery. A few such bursts (lasting anywhere between 20 seconds and one minute) done three times a week can produce dramatic changes. Numerous trials have shown that HIT not only makes people aerobically fitter in a remarkably short time but also metabolically fitter. In particular, it improves the body's ability to process the glucose surge you get after a meal. As someone with a genetic propensity to develop diabetes, this is particularly important.

Early versions of HIT were tough, best suited to those who were already athletic. Modified versions have recently been tested on people who are older, heavier and in less good health, such as those with heart disease. Done properly it is safe, effective and surprisingly enjoyable. It burns more fat than conventional exercise and, best of all, it's over in less time than it takes to drive to the gym. A self-confessed couch potato, I've been doing short versions of high-intensity training for almost a year, with impressive results. During that time I teamed up with journalist Peta Bee. Despite the fact that we have very different attitudes to exercise (she loves it, I loathe it) and she started out super-fit (I wasn't), we bonded over a mutual enthusiasm for HIT. We hope HIT will be a hit.

Fast Exercise by Dr Michael Mosley with Peta Bee, $19.99