Friday, August 10, 2007

Aerobics make you fat?

A few days ago I referred to the Australian study where women doing high intensity intervals - 8 seconds on 12 off - had som excellent results.

I just remembered that I had a note that Alwyn Cosgrove had made an interesting comment on this at his blog.

Aerobics vs Anaerobics and Fat Loss

A few loyal readers will remember a few weeks ago that I hypothesized that interval training would help fat loss, but steady state aerobic training may actually have a negative effect in a fat loss program (here) -(I think that it doesn't burn many calories and may decrease metabolism) on:

I've mentioned this study before - but now the results have been further analyzed and confirmed and after emailing the lead researcher yesterday I received more information.

Trapp EG and Boutcher SH
Fat loss following 15 weeks of high intensity, intermittent cycle training
Fat Loss Laboratory, Faculty of Medicine,
University of New South Wales, Sydney, Australia

Without going through the study line by line (that's for the guys on the internet forums) I'll summarize the findings briefly:
Two groups:

Group One: performed 40 mins of steady state aerobics at 60% VO2 max, three times per week for 15 weeks.

Group Two: performed 20 mins (i.e. half the duration) of interval training (8s on, 12s off - 60 rounds), three times per week for 15 weeks. Group two started at 5 mins total the first week.

Both groups had dietary intake monitored closely.

The steady state group GAINED 0.5kg of fat in 15 weeks.
The interval training group LOST on average 2.5kg of fat in the same time frame.

When two already very lean subjects were removed (BMI was less than 20) - the interval training groups results improved to an average of 3.9kg of fat (Steven Boutcher told me that two women in the interval group lost 8kg of fat).

Again, look at the numbers - the aerobic training group GAINED fat (a small amount). The Interval Training group lost 5-8 times as much fat as the steady state group gained despite training for half the time.

Anyway - I rest my case :)

PS - that's another reason we use metabolic resistance training and interval work in the Afterburn program.

This is the principle that Art Devany mentions in his essay.

"......The body uses fat in the aerobic (ST and lower IT) zone.....linear thinking suggests that to burn fat you should operate in that zone. It would not surprise someone trained to understand the adaptive capabilities of the human body that if you burn more fat the body will find a way to produce more. And this is just what happens when you energy flows over the aerobic pathway—your body releases hormone messengers that signal higher fat production. "


Kt said...

Hey Chris,

Great blog, I find between this blog and Art De Vany's, my whole approach to fitness is changing (I was a total aerobic junkie). I do have a question. Do you think trying to incorporate a large amount of walking (over varied terrains/hills) would help with weight loss, in addition to a few intense exercise sessions (like sprinting) a few times a week? Or would too much walking prove detrimental?

Chris said...

Hi there - thanks for the comment and the compliment forthe blog.

Regarding your question you shoudl maybe have a look at Mark Sission's article - the Case against Cardio.

He advises that over a week a good amont of low intensity exercise - walking hiking etc - should be done plus a a coule of high intensity sprint sessions etc. I think in terms of fitness and boosting VO2 max then high intnsity intervals have proved their effectiveness. But much of life is low level easy activty and we need to do that too.

It is the power law distribution that Art DeVay refers to in his essay - lots of easy stuff and a little very hard stuff, distibuted fairly randomly through the week.

Personally I do a lot of hill walking at weekends in the Scottish mountains - often a 6-8 hours walk; easy daily walks of 30-40 mins and a couple of hard interval or weights sessions keps me fit for that.

As for fat loss I think it is really about tightening diet.