4. How long should I work out to burn FAT?
Description
This article is from the Fitness FAQ, by Jeff Gleixner (glex@cray.com) with numerous contributions by others.
4. How long should I work out to burn FAT?
An aerobic work out should last at least 12 minutes, not counting
warm up or cool down, only the amount of time your HR is within your
Training Zone. The longer and more frequently you do this the sooner
you'll see an improvement (Less Fat..).
Why 12 minutes?
According to Covert Baily this is the amount of time needed for the
body to start producing FAT burning enzymes. It does level off, but
the idea is that you want to get your body to use FAT for energy.
After 12 minutes you start to burn fat at a higher rate.
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Stephen Holt, CSCS holtcscs@supercom.win.net
To quote _Galloway's Book on Running_, "After 5-10 minutes the
percentage of FATs burned rises while the percentage of
carbohydrates drops."
The following graph (please forgive the artwork) is from David
Costill, perhaps the world's foremost exercise physiologist. (From
his book, A Scientific Approach to Distance Running.)
| FAT | f | f | f | f | f c | f c c f | fc c f | c f fc | c f f c | f f c | f c | c | c | c | carbs ------------------------------------ 0 15 30 40 time in minutes
The fact is, after 30 minutes of running, the body burns a
_higher_ percentage of FAT.
From John Galleher
From a Sci.med.nutrition post: at rest the body is burning
65%-80% fat 20-35% glycogen. The body does this to conserve
glycogen. It takes much less oxegen to burn glycogen than
fat (fatty acids). That is why the preferred fuel (from the
bodies standpoint not yours) for heavy exercise is glycogen.
And then the body will replace the glycogen by further food
intake or burning fat later on. The brain requires glycogen
(cannot burn fatty acids) so if you are burning glycogen
long enough (The 12 minutes) the body realizes that it is
going to run out of glycogen if things keep going and starts
to shift over to burning fatty acids to spare the glycogen
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