Can You Really Lose More By Exercising Less?
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?
Let's take a closer look at what happened in the study...
Australian researchers 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 [2]. 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 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."
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's a big part of the cardiovascular workouts
featured in my Fight Fat and Win
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 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 research on which this claim
is based, you'll know
that NONE of the people in the study lost a significant amount of weight.
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 will increase calorie expenditure in the hours after exercise, as will most forms of high-intensity exercise. It's
also been shown to boost
the activity of various fat-burning enzymes [3].
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, the results weren't
quite as exciting as they first appeared.
Here's why...
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 gained 0.5 kilograms (1.1 pounds).
The results are shown in the figure below.
The 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 0.4 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 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.
The interval group also dropped more abdominal fat, although it was a very small (less than 0.2 kilograms) amount.
It's also worth pointing out that subjects in the steady-state group started out cycling for only 10-20 minutes. Over the course of the 15-week study, this gradually increased to a maximum of 40 minutes per workout.
So it's not true to say that the interval group got better results with "half the exercise" as the steady-state group weren't actually exercising for 40 minutes from day one.
Diet
What about diet? How did that affect the results?
Calorie intake was monitored using 3-day diet diaries that were completed at the start and end of the study.
According to these diaries, the steady state group reported a decrease in their calorie intake over the course of the study in the region of 400 calories per day.
Yet despite this reported reduction in calorie intake, the women in this group actually GAINED weight.
The problem here is that self-reporting is a notoriously inaccurate way to estimate
calorie intake. Some studies show that people underestimate their
calorie intake by up to 50% [1]. In other words,
someone who says they are eating 1000 calories per day may really
be eating 2000 calories.
The researchers themselves also point out that their estimates of calorie intake "lack sufficient precision."
"Our estimates
of energy expenditure and intake lack sufficient precision to comfortably conclude that energy balance was
unaffected in the [interval training group]. Thus, it is feasible that
the change in fat mass that occurred in the [interval group] may have been
influenced by unreported changes in diet." |
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.
Here's something else that's very important.
In terms of fat loss, this study doesn't tell us how well interval training compares to more intense steady-state cardio.
This study used moderate-intensity cardio (60% VO2max or around 75% of your maximum heart rate). It's
possible that steady-state cardio performed at higher levels (around 75% of VO2max or 85% of your maximum heart rate) would produce very similar results to interval training.
In fact, a more recent study shows that when high-intensity steady-state cardio is used, it leads to a FASTER rate of fat loss than 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. The interval training used in this Australian
study is similar to the level
III workout in my Fight Fat and Win program.
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.
The fact is that there are MANY different ways to do cardio. All of them have their place at different times and for different people. Don't be duped by the HIIT "propaganda machine" into believing that interval training is the "only way" (or even the best way) to drop fat.
A program that combines resistance exercise, good nutrition AND cardio, be it interval training or simply plain old "vanilla" steady-state cardio, is one that will deliver the best results.
About The Author
 Christian Finn holds a master's degree in exercise science, is a certified personal trainer and has been featured on BBC TV and radio, as well as in Men's Health, Men's Fitness, Muscle & Fitness, Fit Pro, Zest and other popular fitness magazines.
If you're stuck
in a rut with your current exercise and diet plan... fed up with
only losing a pound here and there... or still skinny after months
(or even years) of trying to build muscle and gain weight... click here now for instant access to his step-by-step muscle-building and fat-burning workout routines.
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References
1. 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
2. Trapp, E.G., Chisholm, D.J., Freund, J., & Boutcher, S.H. (2008). The effects of high-intensity intermittent exercise training on fat loss and fasting insulin levels of young women. International Journal of Obesity, 32, 684-691
3. Talanian, J.L., Galloway, S.D., Heigenhauser, G.J., Bonen, A., & Spriet LL. (2007). Two weeks of high-intensity aerobic interval training increases the capacity for fat oxidation during exercise in women. Journal of Applied Physiology, 102, 1439-1447
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