When it comes to weight loss, scientists believe it’s possible to exercise less, and yet lose more weight.
Imagine a world in which those excess kilos simply fall off, without hours spent sweating in the gym. Where you burn more calories and lose more fat in 20 minutes than you could after a week crammed with seemingly endless, time-consuming jogs.
This is the reality of high intensity interval training (HIIT) – an exercise regime that not only works, but one which demands less of your time. And if you think this sounds too good to be true, think again. Because scientists and exercise professionals around the world have built on years of research, and have proven the benefits of short bursts of intensive exercise.
How much exercise do I need?
More than half of all Australian adults are overweight or obese. It’s perhaps not surprising, therefore, that the diet and weight loss industries are thriving. From healthy home-delivered meal plans to the lure of gym memberships and personal trainers promising long-lasting results, we’re overwhelmed with options to help us cut our calories and trim fat from our physique.
But, as an ever-growing amount of consumer spending is directed towards getting thinner and healthier, our waistlines continue to expand, with Australia now the world’s fourth most obese nation. Are we simply eating our way to weight gain, or could it be we’ve simply been getting it all wrong?
According to the World Health Organization, unhealthy diets and physical inactivity are the key culprits for major diseases such as cardiovascular disease, cancer and diabetes. They identify a lack of physical activity as the fourth leading cause of global mortality, accounting for six per cent of deaths globally.
When it comes to getting mobile, the Australian government recommends adults (those aged between 18 and 64) integrate at least 30 minutes of moderate-intensity physical activity on most, preferably all, days of the week. Whilst the health benefits of moderate exercise are plentiful, when it comes to losing weight, an increasing body of research suggests you will do better to cut back on the length of time you commit to exercise whilst increasing the intensity of your workout.
A study published in the Journal of the American Medical Association followed the exercise habits of over 34,000 women. It concluded that it took about an hour a day of moderate exercising to maintain weight. This research is backed up by the findings of the (US-based) National Weight Control Registry, which reported that 90 per cent of people who have successfully lost weight and kept it off exercise on average for an hour a day.
However, this research also tells us that even one hour of moderate intensity exercise every day is not enough to lose weight.
A smarter way to workout
A much more efficient way to exercise – and one that scientific research is suggesting works a lot better both in terms of health benefits and fat burning – is to take part in high-intensity circuit and interval training. High intensity interval training can be applied to any cardiovascular workout, be it cycling, running, rowing or your regular circuits, and refers to short bursts of high intensity exercise periods interspersed with rest or relief periods.
Earlier this year, Sydney scientists reported that sprint training for just 60 minutes a week burns the same amount of body fat as jogging for seven hours a week. For the timepoor, that’s a saving of 180 minutes each week, for the same results.
‘We’ve been searching for about 10 years for the minimum amount of exercise you can do with the biggest health impact factor,’ said Dr Steve Boutcher, the lead researcher.
Dr Boucher, who is an exercise physiologist and associate professor at the University of NSW, believes the high-intensity training regime followed in the study provides the ideal amount of exercise intensity for health benefits, including weight loss, in a short time period.
As part of the program, participants sprinted on an exercise bike for eight seconds, and raised their heart rate to between 80 per cent and 90 per cent of its maximum rate, followed by 12 seconds of slow peddling. ‘In three 20 minute sessions a week, they’re only working hard for eight minutes,’ Dr Boutcher said.
Over the course of 12 weeks, most participants lost an average of 2kg fat and gained 1.1kg of muscle mass in their trunk and legs.
The scientists found that fast sprinting caused the body to release high levels of a specific group of hormones, called catecholamines, which drive the release of fat, especially abdominal and visceral fat, from fat stores so it can be burned by working muscles.
Whilst this study, which was published in the Journal of Obesity and was sponsored by Diabetes Australia, only looked at the effect of sprints on an exercise bike, the same principle can be applied to fast running, skipping, boxing and other high-intensity activities.
When picking your activity, the key is to select something that can increase your heart rate to a high enough level for the body to release catecholamines. According to Dr Boutcher, lower-intensity activities such as swimming and walking would not be capable of achieving the same results. Why does HIIT burn more fat?
Exercise scientists used to believe that ‘steady state’ cardio exercise was superior for fat loss because relatively more fat is used by the body as fuel at lower exercise intensities than at higher intensities. This is why the ‘Fat Burning Zone’ you’ll see on your cardio machine at home or in the gym is marked at just 60 to 65 per cent of your maximum heart rate. In fact, this mythical ‘zone’ is not optimal. You may burn more fat relative to glycogen when you go for a walk, but the total amount of fat lost during a walk is considerably less than if you train at higher intensities.
During these intensive workouts, the fat/glycogen ratio is lower, but you burn much more fat. Add this to the fact that interval training allows you to exercise at very high intensities for a much longer period of time, and you can see why HIIT is such a hit when it comes to weight loss. As an added bonus, some research suggests there’s also an afterburn effect known as excess-post exercise oxygen consumption (EPOC), which means your metabolism and ability to burn calories increases for up to 24 hours after interval training. Compare this to a gentle jog, after which you’ll burn zero calories.
Intervals are better for health, too
Whilst Boutcher’s research focused on the weight loss, a more recent British study revealed that short, sharp bursts of exercise are better at warding off heart disease than longer, less strenuous sessions.
Comparing men who took part in high-intensity sprints on an exercise bike with those who walked for half an hour on a treadmill, Dr Gray from Aberdeen University found that short bursts of intensive exercise spur the liver into taking in more fat from the blood, before storing it, or burning it off. ‘Our study showed that higher-intensity shorter intervals of exercise might be a more effective method to improve health and reduce the time commitment to exercise,’ said Dr Gray.
As obesity continues to affect the nation’s health, the discovery that shorter bursts of activity can achieve outstanding results – both in terms of weight loss and overall health – gives hope that more of us may be inclined to exercise. With lack of time often cited as the main barrier to exercise, the prospect of spending just eight minutes sprinting is surely the couch potato’s dream.
The ‘Tabata’ interpretation of interval training offers an easy way to integrate intervals into your workout regime. The exercise physiologist Izumi Tabata devised an exercise protocol based on 20 seconds of intensive training followed by 10 seconds of recovery for four minutes. Analysis of the results showed both anaerobic and aerobic improvements.
Whilst you can apply the Tabata technique to any exercise, the following exercises are recommended. The key is to give it 100 per cent during each 20 second interval.
Killer sprawls: The sprawl is a full body movement that involves some of the largest muscles in the body. Start with a tuck jump, bend down and move into a push up position. Jump your legs back in and return to standing.
Mountain climbers: In a push up position, bring one leg forwards whilst keeping the other extended. Start the workout by kicking the extended leg forwards, moving the other back. To make the workout harder, keep the front foot floating off the ground.
Split Lunges: Stand with your toes facing forward and your feet approximately one foot apart. Step your right foot out approximately three feet in front of your body. Slowly bend your right knee, lowering your body down to the ground. Push yourself back up to standing. Bring the right foot back to the starting position and repeat with your left foot.
If you have any history of injuries, please consult your physical therapist and personal trainer before performing any of these exercises.
What is Fartlek Training?
Referring to the Swedish for ‘speed play’, fartlek training is a form of interval training that was developed in the 1930s to improve speed and endurance. Now, scientific research suggests Fartlek can significantly speed up the weight loss process.
As fartlek training improves both your aerobic and anaerobic capacity, it has the proven ability to speed up and significantly increase your metabolic rate, which in turn leads to faster, more effective weight loss.
By burning calories above and beyond what you are putting in, your body will then start using its fat stores as a source of energy.
It’s thought that, when it comes to shedding excess kilos, a 25 minute session including irregular bursts of energy is more valuable than an hour of steady intensity, consistent exercise.