This article on the latest “fitness revolution” in high intensity interval cardio training is brought to you with the compliments and permission of my friend and colleauge from the UK, Christian Finn. Christian’s commentary was prompted by the recent news reports of the Australian study (actually not published yet), which claimed that 20 minutes of interval training using 8 second intervals was superior to other forms of cardio and burns three times as much fat. I was going to write about this myself, but I think christian did a brilliant job explaining the truth behind this claim and about HIIT cardio in general.


Can You Really Lose More By Exercising Less?
By Christian Finn
www.TheFactsAboutFitness.Com

 

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.

Boutcher thinks the current government recommendations for exercise are largely ineffectual. “Walking for 60 minutes, seven times a week does not result in much fat loss, usually 1.15 kilograms over 15 weeks,” he says. “For a lot of overweight people this is going to be a revolution.”

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.

C Finn, UK

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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 The Author

Christian Finn holds a masters degree in exercise science, is a certified personal trainer and a regular contributor to Men’s Health, Men’s Fitness and other popular fitness magazines.


www.TheFactsAboutFitness.Com

 


Tom’s Comments

Christian Finn wrote:

“And we still don’t know how well interval training compares to more intense steady-state cardio”

For what its worth, intense steady state, longer duration (35-45 min) frequent (6-7 d/wk) cardio is how i do my cardio for bodybuilding contest prep; tapering off a bit as show gets very close.

The higher intensity, longer duration, steady state stuff works so well once im in the groove of the dietfor a few weeks, that i swear I can see myself getting leaner by the day. By contrast, an hour of walking ( low intensity) brings results, but so slowly that sometimes it feels like watching the grass grow, suggesting to me that low intensitycardio produces results, but at a very slow and linear rate, and that there is an intensity threshold point at which results start coming not only at a higher, but also exponential rate, even steady state sessions.

Shorter HIIT workouts (20-25 min or therabouts, with 60 second intervals), I also find effective, no doubt about it, and I do some shorter HIIT cardio myself. But I find that short HIIT workouts, while definitely effective, do not even come close to fat loss produced by 40-45 min at the highest intensity I can generate.

I think there is a big misconception that steady state and low intensity are one in the same. Granted, intensity and duration are inversely related, but you could do a 45 minute cardio session at a slow casual walking pace, or 45 minutes at the highest intensity you can handle. There is a big difference between the two and this is seldom discussed.

Ironically, nearly every time I mention this comparison of intense steady state work to shorter intense intervals to the die hard HIIT proponents (15-20 min X 3 d/wk guys) they sometimes just laugh and say that more than 20 minutes X 3 days of cardio per week is a waste of time. (At that point, I usually ask them to compare abs with me, LOL)

I could also tell you a story about one of those “tough cases” – a national level female body builder who swore she could “never get totally lean” or “lose stubborn thigh and glute fat”…. until finally i started doing the cardio WITH her to ensure compliance (she was a cardio “slacker,” it turns out)

side by side on a stairmaster or stepmill, we did 40-45 minutes semi fasted (only protein drink + cup coffee) in the early AM… the Fat came off her “by the day” as well…surprise surprise. I have to admit, those workouts were not exactly “fun.” we pushed to the limit for 40-45 minutes nonstop (steady state). I got pretty darn lean myself and she was ripped and made top 5 in an NPC national bodybuilding competition.

I think it’s interesting that one of Christian’s favorite cardio workouts combines aspects of steady state and interval training into one, and lasts a total duration of 35 minutes (25 minutes of modified HIIT) sandwiched between 5 min of warm up and 5 min of cooldown)

I’ve also recently read suggestions by a couple different fitness experts to try a very short HIIT workout – maybe just 10-20 minutes at very high intensity, followed by 30 minutes of low intensity work. It might be interesting to see and hear some results from using this method too.

I’ve noticed the cardio pendulum swinging back to the center a bit lately, as a few more experts are recommending that each type of cardio has its place in the proper context and that a mixture of HIIT and longer duration steady state work might be ideal.

Short sessions of HIIT (20 min or even less) definitely can produce results, and are the time efficient workout of choice for the busy person, but have also been hyped with inflated claims as Christian pointed out, and also promoted with the same religious fervor as mentzer and HIT weight training…

This new 8 second protocol…. well, maybe there’s something to it, but I dont think anyone knows for certain yet what are the optimal intervals for fat loss, and I’d bet that there are a countless number of variations on HITT that all work very well.

– Tom V.

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