Just the other day, I came across a story about another “revolution in weight loss,” with scientists claiming to have devised a workout that burns three times more fat than regular workouts lasting twice as long. According to the story, the researchers found their specific brand of interval training triggers a metabolic response that allows more fat to be burned under the skin and within the muscles. Can you really lose weight three times faster with only half the exercise?

Here, as Kent Brockman would put it, is my two cents…

First, let’s take a closer look at what happened in the study.

Researchers at the University of New South Wales and the Garvan Institute studied a group of overweight women, putting them through a 20 minute cycling regime in which they sprinted on a stationary bike for 8 seconds followed by 12 seconds of cycling lightly [1]. The women performed the workout three times a week for 15 weeks.

“They lost three times more weight than other women who exercised at a continuous, regular pace for 40 minutes,” says University of New South Wales Associate and study co-author Professor Steve Boutcher. The scientists believe the regime would also be applicable to swimming, walking, running and rowing.

Other types of interval training using longer work and rest periods, says Professor Boutcher, are not as effective for overweight people. As far as I can tell, the work-rest ratio (8-second sprint, 12-second recovery) is based on a previous study by the same researchers showing that short work and rest ratios burn more calories than longer (24-second sprint, 36-second recovery) intervals.

So, is this a revolution in weight loss?

Maybe… if you’ve had your head in the sand for the last 10 years.

Using interval training to lose fat is certainly not a revolutionary idea. It forms the core of the cardiovascular workouts featured in the Fight Fat and Win (FFW) programs. And there are plenty of other people who have been writing about it — and using it — for a number of years.

However, even though interval training is both a highly effective and time-efficient way to train, saying that it’ll help you lose weight “three times faster” than regular cardio does (in my opinion, anyway) paint a rather overly optimistic picture about what to expect.

I’ll explain why in a moment.

Yes, I know that interval training is often said to be “nine times” more effective than steady-state aerobic exercise. However, if you’ve actually read the study on which this claim is based (Interval Training and Fat Loss: The Untold Story), you’ll know that neither group in the study lost a significant amount of weight. The aerobic exercise group lost one pound, while the interval-training group lost an average of just 100 grams. And that was after 15-20 weeks of regular exercise.

With all the fuss about interval training and fat loss, you’d think there are dozens of studies to show that it consistently leads to greater fat loss than steady-state cardio. But there aren’t.

It’s true that interval training is a great way to increase calorie expenditure in the hours after exercise. It’s also been shown to boost the activity of various fat-burning enzymes. However, most studies of interval-style workouts have looked at changes in performance and fitness, rather than weight loss.

Studies to track changes in body composition are few and far between, which is one of the reasons this Australian study caught my eye.

However, when I looked at the research in detail (and the paper has yet to reach the pages of a peer-reviewed journal, so I only had access to a short summary of the study), the results weren’t quite as exciting as they first appeared.

At the end of the 15-week study, the interval-training group had lost, on average, 2.5 kilograms (5.5 pounds) of fat. The steady-state group actually gained 0.5 kilograms (1.1 pounds).

So, the actual amount of fat lost in the interval training group wasn’t all that great — 5.5 pounds over 15 weeks, which works out at just 0.37 pounds of fat loss per week. This figure doesn’t really grab your attention like “three times greater weight loss.”

In fact, I can’t actually figure out how the researchers arrived at a figure of “three times greater weight loss,” as the interval-training group lost weight while the steady-state group gained it.

What about diet? How did that affect the results?

Although the women’s calorie intake was monitored using a food diary, self-reporting is a notoriously inaccurate way to estimate calorie intake. Some studies show that people underestimate their calorie intake by up to 50% [2]. In other words, someone who says they are eating 1000 calories per day may really be eating 2000 calories.

So, changes in calorie intake might have been primarily responsible for any weight loss. Or they might have had nothing to do with it. We don’t really know for sure.

And we still don’t know how well interval training compares to more intense steady-state cardio. This study used only moderate-intensity cardio (60% VO2max). To trigger a substantial post-exercise calorie burn, you need to work at around 75% of VO2max, or 85% of your maximum heart rate. It’s possible that steady-state cardio performed at or above this threshold would produce very similar results to interval training.

With all that said, I still think that interval training is a great way to lose fat. It’s something I use myself and recommend to others. In fact, the interval training used in this Australian study is very similar to the level III workout in the Fight Fat And Win (FFW) program, which involves a 25-minute workout sandwiched between 5 minutes of warming up and 5 minutes of cooling down.

However, interval training alone is not a magic bullet, and I think most people would be disappointed losing only 5.5 pounds of fat after 15 weeks of exercise. A program that combines resistance exercise, good nutrition AND interval training is one that will deliver the best results.

References

1. Trapp, E.G. & Boutcher, S.H. Fat loss following 15 weeks of high intensity, intermittent cycle ergometer training. University of New South Wales, Sydney, Australia

2. Lichtman, S.W., Pisarska, K., Berman, E.R., Pestone, M., Dowling, H., Offenbacher, E., Weisel, H., Heshka, S., Matthews, D.E., & Heymsfield, S.B. (1992). Discrepancy between self-reported and actual caloric intake and exercise in obese subjects. New England Journal of Medicine, 327, 1893-1898

About Christian Finn Christian Finn holds a masters degree with distinction in exercise science. He has lectured at universities and private training organizations around the United Kingdom on fitness training, weight loss and the effective use of supplements. If you live in the UK, you may have seen Christian in the BBC TV series Body Hits. Christian was also the fitness expert for the Bravo TV series All About Men. You can find Christian's articles published in numerous magazines, journals and websites worldwide, including Men's Health, Men's Health Muscle, Fit Pro, CAM magazine, Image, Zest, and Body Life magazine. You also might have seen Christian featured in the July 2004 issue of Muscle & Fitness. A tireless researcher, Christian has lost count of the number of hours he has spent reviewing the latest scientific research on diet and exercise for the benefit of his readers. Christian’s research on high-intensity intermittent training has been published in the online journal Sport Science (March 2001). As a certified personal trainer, Christian has spent more than a decade working with people of all shapes and sizes, as well exercising regularly himself for over 15 years. You can subscribe to Christian's FREE newsletter at www.TheFactsAboutFitness.Com and you can visit his members only website at: www.ChristianFinn.Com