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lamchopthis
07-11-2006, 10:55 AM
I'm just wondering: is there an order to the way calories are burnt for energy?

For example: carbohydrates, protein, and then fat?

Captainhowie175
07-11-2006, 11:04 AM
yes, carbs are always burnt first, they are the brains primary source of energy. when you eat more carbs than you can burn, you stop burning fat and you metabolism goes into overdrive to burn them off, if its paired with fat you will store the fat, and thats only if you over eat. as far as protein goes its not a clean burning fuel you want to use protien to rebuild your muscles not burn it off. 30% of the protien you eat is always burnt off because of thermogenisis 8% for carbs and 2% for fat. so in short carbs and fat should always be used as fuel, protien for tissue repair. If you prasctice good portion control you really can use it to either lose or gain weight very effectivly.

PickItUp
07-11-2006, 11:06 AM
I'm just wondering: is there an order to the way calories are burnt for energy?

For example: carbohydrates, protein, and then fat?

Yes, there is an order...I am not 100% sure what it is and what the possible deviations are...but here goes:

1. Free Floating Blood Sugar (glucose) is used first...if you just ate something, that will be used for fuel rather than storing it as energy.

2. Muscular Glycogen is tapped next. This is a form of glucose that the muscle stores for immediate energy usage.

3. Liver Glycogen is third in rotation. This is glycogen stored in the liver for use by any muscles that need it. Muscular glycogen can only supply energy to the muscles that it is stored in (or so I am told)

4. Fat stores. Finally, teh body turns to fat deposits for energy...

Now, what I have asked several times on this forum, and have yet to be answered...is:

Is that order of operations set in stone? Do we have to completely deplete muscular and liver glycogen before any fat gets burned? I would like to think of the body as a system that draws energy from all its sources in real time. Instead of waiting for the liver glycogen to be depleted...I like to think that the body starts using up fat tissue to supply energy before it completely runs out of liver glycogen. I am not 100% on this as stated earlier.

d77
07-11-2006, 12:23 PM
Is that order of operations set in stone? Do we have to completely deplete muscular and liver glycogen before any fat gets burned? I would like to think of the body as a system that draws energy from all its sources in real time. Instead of waiting for the liver glycogen to be depleted...I like to think that the body starts using up fat tissue to supply energy before it completely runs out of liver glycogen. I am not 100% on this as stated earlier.
I agree with you, although I'm also not quite sure. If your body used energy in a specific order than the only way to burn fat would be morning cardio and cardio after a workout (basically work with all other energy sources burned).

PopeGregorius
07-11-2006, 01:48 PM
The fastest buring food is alcohol (7 cal/g)l, which is oxidised to acetaldehyde & eventually to acetic acid.

The brain prefers glucose but can happily survive on ketones. Other sources are free fatty acids
http://en.wikipedia.org/wiki/Fatty_acid_metabolism

Also see the Krebs cycle
http://en.wikipedia.org/wiki/Citric_acid_cycle