How much exercise do we really need?

16:00, Feb 10 2014
WORK FAST & HARD: Well he's obviously just had a very intense 20 seconds.

In my prime as a compulsive recreational runner, I pounded the pavement almost every day for years to clock up the kilometres. It culminated in a marathon that left me feeling exhilarated, but also a tad tired of running.

I loved the endorphins rush and the way it kept me fit and lean, but it did leave me awfully sweaty and chewed up a lot of time, which I no longer seem to have in surplus.

We all know we need to exercise to aid good health, but is it really necessary to push our bodies for prolonged periods, like mice on miniature wheels in laboratories, just to stay slim and healthy? According to the latest popular school of thought, there's no need.

It's a cheat's paradise. Scientists and those in the medical know say feeling good, fit and healthy from exercise requires a mere few minutes of intense exercise just three times a week, instead of the long, slow burn that most of us feel we must endure.

British medical doctor and BBC journalist Michael Mosley - who popularised the 5:2 intermittent fasting diet for weight loss - now advocates high-intensity exercise bursts of just 20 seconds at a time to add up to a minute, three times each week, to keep good health. The idea is to ramp up your heart rate quickly to prompt your body to increase its aerobic fitness and ability to process glucose.

Australian exercise physiologist Steve Boutcher, an associate professor, has been studying such seemingly smart exercising for a decade at the University of NSW. His research shows that 20 minutes of intense interval sprints on an exercise bike, three times a week, will eliminate belly fat.


"Diets do not work in the long term for the great majority of people; the stuff we want to lose is the stuff we can't feel - it's devilish," Boutcher says of the insidious visceral fat that surrounds our organs but doesn't always protrude externally as a worrisome girth.

Like Mosley, Boutcher practises what he preaches and takes to his exercise bike. He says adopting this scientifically backed sprinting regimen - which includes drinking green tea before exercise to aid fat burning, and switching to a Mediterranean eating plan - keeps fat at bay. "Green tea ingestion results in enhanced fat burning by blocking enzymes that degrade norepinephrine, a major fat-burning hormone," Boutcher says. Women in Boutcher's studies lost 9 per cent of total body fat and 6 per cent of visceral, or belly, fat after completing a 12-week interval sprinting program that included a Mediterranean diet. Men lost 17 per cent of belly fat.

The sessions may be quick, but the key to long-term success appears to be dedication to the task, alongside a healthy diet and lifestyle. "It takes six weeks of interval sprinting exercise to see a significant reduction in waist circumference," he says. The mechanisms behind this include increased fat burning, more muscle mass and reduced appetite after eating.

Exercise bikes were used in the studies, but Boutcher says other high-intensity interval exercises - rowing, walking, stair climbing, running, boxing, skipping, swimming and circuit work - can also achieve good results. He suggests an eight-second sprint, then a 12-second recovery, repeatedly, for 20 minutes at light, moderate and hard intensities.

"The workout that the leg muscles receive is likely to be the major reason why all studies that have examined cycle interval sprinting and glucose metabolism have shown that it reduces insulin resistance," Boutcher says. "This finding has major implications for the prevention of type-2 diabetes, which has been shown to be a disease of the legs and liver."

It's not entirely clear why consuming a Mediterranean diet is effective, but it may be because it is rich in antioxidants, folic acid and healthy fats. It involves eating vegetables, beans, nuts, wholegrains, cereals, fish and seeds, as well as olive oil and omega-3 fats.

Boutcher has written a book, 20 x 3, about his research. He also says there are other factors impeding fat loss, including lack of sleep and high stress levels: "People who are successful in keeping fat off eat healthily, exercise regularly and always eat breakfast."

- Daily Life