Australasian Science: Australia's authority on science since 1938

The Fast Way to Lose Fat

By Stephen Luntz

Short sprints should replace steady exercise.

The path to weight loss is seldom easy, but A/Prof Steve Boutcher of the University of NSW School of Medical Sciences believes it might be easier if short sprints replace steady exercise.

Boutcher asked a group of obese men to ride exercise bikes intensely for 8 seconds, followed by 12 seconds of gentle peddling. This was repeated 60 times and performed three times per week for 12 weeks.

Participants lost 2 kg of body fat over the period. More significantly, most of this was in the form of abdominal fat, which is considered more dangerous for cardiovascular conditions than fat on the limbs.

Even more interestingly, the men gained 1.2 kg of muscle, which usually requires far more extensive exercise.

A previous study conducted on women produced average weight losses of 2.5 kg over 15 weeks, with larger losses for women who were overweight at the start of the trial.

“Other studies using aerobic exercise, such as continuous jogging, have found that the amount of exercise needed to produce a similar decrease in visceral fat was around 7 hours per week for 14 weeks,” Boutcher says.

Similar benefits were also achieved with slightly longer sprints adding up to the same 20-minute cycle, but Boutcher says longer sprints are generally more painful. Intense bursts punctuated by gentle exercise also produced results when running, rowing, boxing and climbing stairs, but Boutcher says rowers benefited most from slightly longer sprints. Walkers and swimmers were less successful at adapting the program.

Boutcher says it is unclear why sprints that punctuate gentle exercise achieve such dramatic results. However, he believes it is important to keep heart rates above 150 beats/min and that the body produce catecholamines, a class of hormones that includes adrenaline. Fast limb motion appears to play an important part in this, making the speed with which participants cycle more important than the resistance they overcome.

Boutcher has published a series of papers over a number of years on the benefits of short bursts of exercise, chasing the greatest weight loss for the least time spent exercising.