This is the other lifestyle change I have recently embraced and written a book about. Like the Fast Diet (see page 4) it sounds like a radical idea, but is soundly science based. Now, everyone agrees that getting more active will add years to your life (around 2.2 years, to be exact) and will significantly reduce your risk of developing a range of chronic diseases, from cancer to heart failure, dementia to diabetes.
Exercise will help you sleep better, improve your mood and even perk up your sex life. According to the well-regarded Mayo clinic in the US (www.mayoclinic.org/exercise/ART-20048389), "Regular physical activity can lead to enhanced arousal for women. Men who exercise regularly are less likely to have problems with erectile dysfunction than are men who don't."
The recommended level is 150 minutes a week, despite the fact that less than 20 per cent of us do anything like that. The most commonly cited reason for not doing more is lack of time. That has certainly been my excuse.
So a while ago I began looking into a radically different approach to exercise called HIT (High Intensity Training). The idea is that instead of trying to shed weight and get healthier by jogging in the rain for hours, you can get many of the more important benefits of exercise from as little as three minutes of HIT a week.
Although HIT has been developed in labs around the world over the past decade, the principles behind it are not new. In the 1950s in Britain, a young medical student, Roger Bannister (left), was determined to run a sub four minute mile. The trouble was, as a busy student he didn't have lots of spare time for training. So he would go down to the track and do interval sprints. These consisted of running flat out for about one minute, then he would jog for 2-3 minutes before doing another one-minute sprint. He would repeat this cycle 10 times, then head back to work. Since he rarely bothered with much in the way of warm-ups or cool-downs, the whole thing normally took less than 35 minutes. In May 1954, he became the first person in the world to break the four minute mile. Since then, almost every middle distance runner has done interval sprints as part of their training.
Jamie Timmons, professor of systems biology at Loughborough University, did interval sprints when he was a student athlete. Since then he has spent many years researching the benefits of what has come to be known as HIT in normal people.
When we first met, he assured me that three minutes of HIT a week had been shown to improve the body's ability to cope with sugar surges (metabolic fitness), and how good the heart and lungs are at getting oxygen into the body (your aerobic fitness). Nobody really knows why, but these two measures are great predictors of future health. Intrigued, I had blood taken and went through some baseline tests to assess my starting point, fitness-wise. Then I began to do HIT.
The version I chose was very simple. I got on an exercise bike, warmed up by doing gentle cycling for a couple of minutes, then started to pick up the pace. At the same time I increased the resistance on the bike, pushing the dial to one of the highest levels, so I was going flat out against almost maximal resistance for 20 seconds.
I then cycled gently for a couple of minutes, long enough to catch my breath, then did another 20 seconds at full throttle. Another couple of minutes gentle cycling, then a final 20 seconds going hell for leather. And that was it. In no more than six minutes my exercise for the day was complete.
I did three sessions of HIT a week for fourweeks (12 minutes of intense exercise in total) and then went back to the lab to be retested.
The first surprise was the effect it had on my insulin sensitivity. This is a measure of the amount of insulin your body has to produce in response to a sugar surge to get that blood sugar back down to normal. As a borderline diabetic, insulin sensitivity is very important to me. But it is something everyone over 40 should have tested, as even slightly elevated levels are associated with increased risk, not only of diabetes but dementia and some cancers. Broadly, the less your body has to produce, the better.
After 12 minutes of intense exercise my insulin sensitivity had improved by a remarkable 24 per cent, something you would be unlikely to see after many hours of conventional exercise. It was extremely satisfying.
But although I was able to cycle longer and harder, I didn't see the 10 per cent improvement in aerobic fitness that typically happens when people do this regime
Why not? Well, it turns out that when it comes to aerobic fitness I can blame my parents. As part of the screening I also had a genetic test which revealed that, like 20 per cent of the population, I am a so-called non-responder when it comes to aerobic fitness. This means that however much exercise I do, and in whatever form, I will never become incredibly fit. It could also help explain why I have never been keen on long distance running. Or even short distance running, for that matter.
Despite this, I have continued doing HIT because of the other benefits, which include improvements in my mood, metabolic fitness and appetite control.
I've found, and numerous studies support this, that doing HIT has a significant effect on the number of calories you eat over the next 24 hours after you have done the exercise. This helps explain why, although it is so short, it seems to be more effective at helping people cut their weight than conventional exercise.
HIT is a shock to the system and the stress caused by HIT also leads to the release of large amounts of catecholamines, which are hormones, like adrenaline and noradrenaline, that target fat cells, particularly those in the abdomen.
Not everyone is going to enjoy pushing themselves really hard, even if it is only for 20 seconds. Yet in trials most people say they prefer it to conventional exercise, not least because it is over so quickly.