Is this a myth ?

B

Bernard

Cathlete
Hi everyone,

When I learnt the basics of exercise physiology, 11 years ago, we were learning at the time when cardio funk hit the scene, and it was everyone do cardio funk, because it is low impact and burns fat, etc. And we were taught that high impact doesn't burn fat because it burns carbohydrates instead.
Please can anyone tell me if views have changed since I was at college, and that yes, high impact aerobics does indeed burn fat, as effectively as low impact aerobics ?

Many thanks

Anna
 
[font size="1" color="#FF0000"]LAST EDITED ON Sep-26-02 AT 11:10AM (Est)[/font][p]Hi Mariela,

What does BUMP mean ? Please explain ! (LOL) I have a bump around my waistline (not a baby bump before anyone wonders if I am expecting !):7

anna
 
Sorry. It means that I want to see the answer for this question too. It also keeps your question in the front page (page #1 of the forum, not with the old questions). Does that make sense?
 
I'm only repeating what I hear another instructor say on her low impact hi/lo videos, but according to Charlene Prickett, an instructor for like 20 years or so, she says, "True, low impact and lower intensity aerobics burn fat as fuel, while higher impact and higher intensity aerobics burn carbohydrates for fuel, BUT, your fat stores are what replenish the carbohydrates burned, plus, higher intensity aerobics burn more overall calories on the whole, so you end up burning more fat in the long run." Not her exact wording, but the "jist" of what she says.

Perhaps someone in the field will add on or tell us if this is true, but this is what Charlene claims on several of her videos.

Donna
 
[font size="1" color="#FF0000"]LAST EDITED ON Sep-26-02 AT 01:30PM (Est)[/font][p]What Donna posted previously is exactly true. With lower intensity exercise, fat is the primary fuel because there is adequate oxygen available to burn it. You are still burning carbohydrates but a lower percentage of them. And, for all the low-carb, no carb fanatics out there, carbohydrates are REQUIRED to burn fat, otherwise you get incomplete fat breakdown which leads to ketosis--contrary to what Atkins says, ketosis is NOT a good thing! Anyway, bumping up the intensity forces the body to switch to carbs as the primary fuel because oxygen is getting used up more rapidly and the body cannot enter the fat burning chain of events with insufficient oxygen. While low intensity exercise will burn fat primarily for energy, the calorie expenditure will be less unless you exercise for a longer period of time. Higher intensity will lead to a greater overall expenditure of calories, of which a percentage will be fat.

Example: 100 calories burned at low intensity--50% fat burned =
50 fat calories burned.
200 calories burned at high intensity--30% fat burned = 60 fat calories burned.

These are just numbers and percentages I pulled out of thin air to illustrate the point. These are not the actual percentages of fat burned with the difrerent types of exercise.

Don't feel "stupid" if you still do not get this theory. I took an exercise physiology class a few years ago and did my thesis paper on High intensity exercise as the better way to burn fat. My professor gave me an "A" and commented that I had taught her something new. It doesn't help that the cardio machine manufacturer's perpetuate this myth by still labeling lower intensity programs as "fat burning" and placing target heart rate charts with heart rate zones listed as "fat burning".
 
Thanks Beets and Donna,

You have both explained this extremely well, it is clearer in my mind now. I won't feel guilty in future for doing high impact instead of low impact, because now I know I will still be burning fat which ever impact I go for.

Many thanks

Anna
 
Here's where people really get confused. The body virtually NEVER burns just one source of fuel. At rest, the major fuel source is fat, with very high intensity exercise, the major fuel source is carbohydrates, and in cases where there is inadequate carbohydrates available, the body breaks down protein to build glucose.

At very low intensity level activity--leisure walking, light housework--fat provides about 70% of the calories needed. As intensity increases, the PERCENTAGE of fat used decreases and the PERCENTAGE of carbohydrates used increases. Lower intensity cardio (at approximately 60% MHR) will use approximately 60% fat, 40% carb mixes. As the intensity goes up, the percentage shifts to utilize predominantly carbohydrates.

The reason for this is that the body is never metabolizing fuel totally aerobically nor totally anaerobically--there's always some of both happening. The harder you work, the less able your body is to provide adequate energy through aerobic means. Since fat can only be metabolized aerobically to provide fuel for exercise, the harder you work, the more the body has to rely on anaerobic metabolism of glucose--since the body's ability to take in oxygen is limited, when you approach those limits, anaerobic mechanisms have to kick in. The fitter you are, the harder you will be able to work while being able to provide energy through primarily aerobic pathways.

Here's the catch--although you burn a higher percentage of fat at lower intensities, the overall number of calories burned in high intensity exercise is greater. 60% of 200 calories is less than 40% of 400 calories, so for a given amount of time, working at a higher intensity can result in more total calories being burned as well as more fat being burned.

There are reasons for working at lower intensities, also. I'll stop here, though, before I write a book!
Maribeth
 
Thanks Maribeth,

That was really interesting, you have amazing knowledge ! This explains why Cathe's workouts are so fantastic at helping people with their weight loss goals and fitness goals. I have to say I was getting confused because I couldn't work out why so many were having weight loss success with Cathe's high impact workouts, but now I see why !
I am though very curious as to what the benefits are for working at lower intensities ? Please go on as this subject is facinating.

many thanks

Anna
 
I've read some great books by a man called Covert Bailey. In one of his books (Smart Exercise) he goes into detail on how our bodies work when we're working out. Check him out at the bookstore or library.

Hélène
 
There are equations that estimate the number of calories burned based on the intensity of the activity and the body weight of the participant.

Covert Bailey is FANTASTIC!!! He has a true gift for taking complex biochemical processes and making them super easy to understand. He also knows that the bottom line for changing our bodies for the better isn't diet, but exercise. I highly recommend his books and videos to anyone!
Maribeth
 
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