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.
I now combine HIT with a very simple strength and flexibility regime which, though it takes less than 10 minutes, three times a week, has led to some impressive biceps and the beginnings of a six pack.
So how can you get so much change in such little time? Part of the explanation is that HIT makes your muscles produce new and more efficient mitochondria, the tiny powerplants that convert glucose into useable energy. The more mitochondria you have, the more power they produce and the more fat and sugar they consume.
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.
And the good news is that scientists like Jamie have developed a gentler version, the 60 second workout.
The 60-second workout
The basic principle, rather like Roger Bannister's training method, is to alternate 60-second bursts of activity with 90-second recovery periods – i.e. one minute on, 1 1/2 minutes off. It can be done cycling or running, though it helps if you are able to adjust resistance. In the case of running or cycling outdoors this means finding a hill to run up.
You might think that 60 seconds of HIT has to be tougher than 30 seconds, but this version is not.
The key difference is that you don't push yourself quite as hard. Instead of going flat out, you exercise for a minute at about 90 per cent of your best effort, aiming to push your heart rate up to around 150 beats per minute.
Researchers from Metapredict (a group of exercise academics) have been testing this approach in the largest study of its kind – involving more than 160 volunteers – and they have found that this less demanding approach still has big benefits. Beginners should start with 2x1 minute, going up to 10x1 minute if you are really fit.
How I do it
1. Put the kettle on.
2. Get on the exercise bike and do a couple of minutes of gentle cycling, against limited resistance.
3. After about two minutes begin pedalling fast, then swiftly crank up the resistance.
4. The amount of resistance you select will depend on your current strength and fitness. It should be high enough that after 40 seconds your thighs begin to burn and the speed at which you are pedalling slows, simply because your muscles are fatigued and you cannot keep going at that pace.
5. If, after 50 seconds, you can still keep going at the same pace then the resistance you've chosen is not quite high enough. It mustn't, however, be so high that you grind to a complete halt. It's a matter of experimenting.
6. After your first burst, drop the resistance and do a couple of minutes of gentle pedalling to catch your breath and let your muscles recharge.
7. Then, when you feel ready, do another minute burst.
8. Do the whole thing as many times as you feel able, but start with two and build up gradually over many weeks
9. Finish with a couple of minutes of gentle cycling to allow your heart rate and blood pressure to return to normal before stepping off the bike and having a cup of tea.
How to get your HIT while running
You don't have to do HIT on an exercise bike. You can add it into a normal cycling routine, do it while swimming, or as part of a run.
My co-author of Fast Exercise, Peta Bee, loves running and gets her HIT this way. She starts by running at a moderate pace for 5-10 minutes and then performs a one minute sprint, preferably up hill. She then jogs for a couple of minutes to recover before doing the next sprint. She finishes with a five-minute gentle jog.
Those short bursts are tougher than you might think. If you do them properly with pumping arms and fast leg speed, you will feel your thighs burn and your heart rate soar- which is a positive thing.
But is it safe?
A year ago the popular BBC broadcaster, Andew Marr, had a debilitating stroke some hours after doing a prolonged and vigorous workout on a rowing machine.
So did the exercise cause the stroke? It is certainly possible that the prolonged and vigorous movement involved in working out on a rowing machine could have caused sheering damage to previously weakened blood vessels in his neck, causing one of them to tear. He had previously had at least one silent stroke and was under a lot of stress; stress is a significant cause of stroke.
It is also possible that his stroke had little to do with the workout, as strokes in people with pre-existing blood vessel damage can happen at any time and be triggered by something completely innocuous, from simply twisting your head to sneezing.
The forms of HIT that I've tried do not involve prolonged exertion and have been extensively studied to ensure they are safe. These studies include trials done with nearly 5,000 patients who have a previous history of heart attacks and strokes.
If you are frail or extremely unfit it would be wise to have a medical check up before starting any form of exercise, but don't use that as an excuse not to start. You can get a dose of HIT while walking or even from climbing the stairs. The benefits greatly outweigh the risks.
1. More is better
Although exercise is good for you, most of the benefits come from the first 20 minutes – during which time genes like lipoprotein lipase get switched on. These genes help suck the fat out of your blood and deposit it in your muscles where it gets burnt as fuel. This reduces the amount of fat circulating in your blood and your chance of having a heart attack.
Research shows that if you are a slob and become more active for 20 minutes a day then that will, on average, buy you an extra hour of life. Or about two years, over a lifetime. But the benefits of doing more exercise, at least in terms of life expectancy then drop off dramatically.
2. You must stretch before exercising
It's widely believed that static stretching – the kind that involves holding a movement, such as bending over and touching your toes – makes your muscles more flexible, primes them for activity and reduces the chance of injury. Yet when Dr Ian Shrier, of the Centre for Epidemiology at the Jewish General Hospital in Montreal, reviewed the evidence on pre-workout stretching for The Physician and Sports Medicine Journal several years ago, he found that stretching immediately before a gym session led to a reduction in muscle power and had no noticeable effect on reducing injury. Shrier, a past president of the Canadian Academy of Sport Medicine, recommends dropping stretches from warm-ups.
3. A proper cool down will prevent DOMS (Delayed Onset Muscle Soreness):
Another popular myth is that cool-down stretches will stop your muscles from becoming sore by flushing out lactic acid, one of the so-called waste products of exercise.
Most of us, I'm sure, have been told that it is the build-up of lactic acid that makes your muscles tired. This is nonsense. Strenuous exercise will lead to greater production of lactic acid but the reason this happens is because lactate is needed as a fuel. Without it you wouldn't be able to push yourself as hard as you do.
The soreness you get after exercise isn't caused by a build-up of lactic acid, but by minor damage to muscle fibres. The only remedy is rest.