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Jane
11-23-2001, 06:49 AM
I tried searching through the forums to try and learn what liver and muscle glycogen is, but there doesn't seem to be one clear-cut explanation anywhere. Can someone help me out with a link or a couple of sentences? Also, what is the capacity and how long does it take to deplete stores? Thanks!

The_Chicken_Daddy
11-23-2001, 07:01 AM
Carbs = Glucose

Stored Glucose = Glycogen

There are two places the body can store glucose. It can either store it in muscle or in the liver. Liver glycogen stores can hold about 100g of carbs. Normally, with carbs if liver glycogen is full then the extra carbs will be able to go to muscle glycogen where they will be stored in the muscle instead of fat.

If the liver and muscle glycogen stores are both full then excess carbs end up being stored as fat.

one type of carbs, fructose, cannot be stored in the muscles, so if liver glycogen is full then rather than the extra fructose being stored in muscle it will go straight to fat. But don;t be put off fruit [source of fructose] just eat fruit for breakfast, because at this time liver glycogen will not be full and the fructose will simply replenish liver glycogen instead of being stored as fat.

Jane
11-23-2001, 07:10 AM
thanks, that was nice and simple. how much carbs does it take to fill both muscle glycogen? and how long does it take to deplete muscle glycogen, liver glycogen, and both together?

The_Chicken_Daddy
11-23-2001, 07:14 AM
How big are your muscles? :)

YatesNightBlade
11-23-2001, 07:55 AM
Originally posted by The_Chicken_Daddy
one type of carbs, fructose, cannot be stored in the muscles, so if liver glycogen is full then rather than the extra fructose being stored in muscle it will go straight to fat.

I don't agree with this.

Your Cells need one souce of chemical to function Glucose ..... all things are converted to this, be it bread, oats, fruit or even protein (at times). The body cannot run on Fructose .... it must be converted first. This is one reaons why fructose is lower GI then something like Glucose.

Tryska
11-23-2001, 07:58 AM
fructose can't be converted though, sweetie. it's a simple sugar.

Alex.V
11-23-2001, 09:11 AM
Sure it can, babycakes.

http://www.med.unibs.it/~marchesi/fruc_gal.html

Simple sugars are regularly converted in the body.

The_Chicken_Daddy
11-23-2001, 09:11 AM
Yates, the reason why fructose has a lower GI value than glucose is most likely because of the fibre acting as a buffer.


Btw, i am pro-fruit.

Tryska
11-23-2001, 09:16 AM
wait...so fructose can be converted to glucose.....or rather to glycogen....which gets stored in the liver......but not blood glucose, right? and blood glucose is what gets stored as fat.

it's been so long since i've read up on this stuff.....

Alex.V
11-23-2001, 09:19 AM
Fructose in the absence of fiber will still have a very small impact on blood glucose (therefore insulin) levels. (unless insulin is already elevated, in which case fructose will have a significant impact. Go figure.)

Alex.V
11-23-2001, 09:24 AM
Fructose can be converted to glycogen in the liver. It can also be converted to f6p in the muscles, which most people seem to forget. I have a feeling that people generally oversimplify carb metabolism by saying "Glycogen/glucose or fat". Those are the end products, yeah, but there are lots of steps in between....

Tryska
11-23-2001, 09:32 AM
well for me, i worship the insulin response at this juncture...so i don't pay a whole lot of attention to fructose or lactose for that reason......so y'all are prolly right, and i'm getting my properties mixed up.

Wizard
11-23-2001, 09:40 AM
Originally posted by Belial
Fructose can be converted to glycogen in the liver. It can also be converted to f6p in the muscles, which most people seem to forget.

Very imprortant info indeed.

I have noticed that the majority of people believes that fructose can't be converted to glucose in the liver but it's a big mistake.
I was confused too about whether it's right or wrong but after asking a guy @ the gym (he's a dietitian),I'm sure that it's right.

The_Chicken_Daddy
11-23-2001, 09:40 AM
Originally posted by YatesNightBlade


I don't agree with this.

Your Cells need one souce of chemical to function Glucose ..... all things are converted to this, be it bread, oats, fruit or even protein (at times). The body cannot run on Fructose .... it must be converted first. This is one reaons why fructose is lower GI then something like Glucose.

Yates, when the liver is full fructose is metabolised differently to glucose or starches in that it will be converted to triglycerides. This causes a rise in blood fats and thus, more fat is stored.

Again, i'd like to re-iterate that i am Pro-Fruit but only in moderation[ie one apple, one banana and maybe an orange a day], and only during the first half of the day but not for the carbs, only for the vitamins, phytochemicals and all the other nice things they have. During the second half the green veggies come out to play.

Wizard
11-23-2001, 09:43 AM
I have also to mention that fructose can raise metabolism by aiding in the conversion of T4 to T3..

I only eat an apple every day but I may add one more serving.

body
11-23-2001, 02:36 PM
Fructose is aborsbed sloqwly then metabolized to acetyl CoA via a insulin independant pathway therefore a rise in insulin does not occur. However its use can increase plasa triglycerides.

frucotse has a low Gi as due to fructokinase convertes it to fructose-1-phosphat(F1p). it does not go via insulin pathway for conversion so the GI does not go up.

the doc
11-26-2001, 06:09 AM
fructose, from fruit, honey, or table sugar (1/2 of which is fructose) is processed differently from glucose. The liver has a special process to deal with it in an insulin independant pathway (thus why frutose, sucrose/table sugar/ and lactose all have lower GI) which leads to its preferential storage as liver glycogen. As belial said, some can be converted to fructose 6 phosphate in the muscles, but to a much lesser extent. Remember all blood goes from the intestines to the liver -thus allowing the liver to detoxify among other things (also the reason why for instance cocaine or anabolic sterioids are very poor oral drugs)- here in the liver glucose is given a "free pass" so to speak whilst fructose and galactose (from lactose) are processed and stored as glycogen in the liver