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 e-mails.
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, done three days a week.
With workouts requiring a minimum 40-second and maximum eight-minute bursts of all-out effort, the promise is that you can lose half a stone or more in the four weeks it takes to complete a programme. What's more your body will look leaner and more toned as fat levels plummet and strength improves. And, as a bonus, your health improves.
The [other] great benefit of Fast Exercise is practical: it can be slotted into a busy life with relative ease. You can, if you really want, do Fast Exercise in your normal clothes, not even bothering to change into trainers.
[Like Dr Mosley's Intermittent Fasting diet, the four-week plan for Fast Exercise adopts a 5:2 approach of five days working out and two days rest.
Exercises suitable for HIT include skipping, indoor rowing, running, stair running or cycling.]
For those who somehow missed the excitement, the Fast Diet -- often called "the 5:2" -- is a celebration of intermittent fasting, also known as IF.
Instead of aiming for slow, steady calorie restriction, the approach that's recommended by sensible dietitians and which most people find impossible to stick to, with IF you slash your calories, but for only a few 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 numerous other health benefits. "It will be huge", my co-author Mimi announced, as we sipped our cups of calorie-free tea.
She was of course right. As well as numerous doctors, politicians and a Nobel prizewinner there have been mentions from the likes of Hugh Fearnley-Whittingstall ("I find myself beguiled, for the first time ever, really, by a new diet"), and the actor Benedict Cumberbatch ("you have to, for Sherlock").
I have lost 10kg, a few inches round 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 round to throwing out.
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.
Intermittent fasting won't suit everyone, but it worked for me. Not only did I lose a lot of fat (four inches off my waist, two 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, during my fast year, 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 intermittent fasting, 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. Like intermittent fasting, HIT 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 period of time but it also makes them 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 to me.
The early versions of HIT were tough, best suited to those who were already quite 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 started out from different positions (she was super-fit, I wasn't), we bonded over a mutual enthusiasm for HIT and wanted to spread the word.
The result is Fast Exercise. Written for those with an interest in their bodies and too few hours in the day, we hope HIT will be a hit. 2014?
Bring it on.