On Jan 17, 2006, at 2:10 am, Todd Moody wrote:

> Ashley Moran wrote:
>
>> Thanks for the explanations Todd.  You seem to know a lot about  
>> this-  is it your job?
>
> Nope, and for that reason you should question everything I say.   
> This is just one of my...hobbies, I guess you could say.

Well that makes you more qualified than most doctors and  
nutritionalists so I'll listen to what you have to say :D



> Yup, that sounds right.  Of course, even when glucose isn't low,  
> there is normally some fat-burning going on all the time.  Many  
> cells can and do use both glucose and fat for fuel.  But yes, when  
> you stop eating carbohydrate, first you'll draw on your glycogen  
> reserves (glycogen is actually a starch, but it's converted back to  
> glucose, like other starches), and since you're not eating carb to  
> replenish them, they'll run out (near enough.  I think the liver  
> doesn't allow them to empty out completely but keeps a small  
> emergency supply).  At that point, those cells that can burn fatty  
> acids will do so, and the liver will increase its production of  
> ketones from fat as well, and those tissues that can use ketones  
> instead of glucose will do so.  In short, your metabolism goes into  
> glucose-sparing mode.  At the same time, your liver also initiates  
> gluconeogenesis to provide some glucose from protein.  The  
> production of ketones from fat uses energy, so some of the calories  
> in the fat are actually "wasted" by the liver in making the  
> ketones, which means that the liver's metabolic rate goes up, in  
> effect.
>
> People who start out on ketogenic diets may well find that they  
> have no fight or flight reserves for a while.  They may feel  
> sluggish for a week or so.  But as more tissues that can burn fat  
> do so, as those that can burn ketones do so,  the actual demand for  
> glucose goes down.  It doesn't happen overnight.  These people will  
> also become more efficient at gluconeogenesis, so their glycogen  
> reserves will be gradually replenished.  In short, they achieve a  
> different metabolic equilibrium.

This makes a lot of sense.  Assuming this is all correct it means  
that low glycogen should be just a withdrawl symptom from excess  
carbs, and that it will be replenished as your body adapts to  
ketosis.  I assume that glycogen is replenished much more slowly from  
glucogenesis than from dietary carbs, hence the dubious advice that  
even low-carb dieters should "carb-up" (I just googled this and  
apparently doing so seriously inhibits fat burning).

I read somewhere that exercise and extended ketosis both push up your  
aerobic limit so that you can do more strenuous exercise while still  
burning fat.



> People who consume a lot of carbs are constantly putting their  
> bodies in a state where all that incoming glucose must be dealt  
> with.  So every cell that is capable of using glucose for fuel does  
> so, and fat-burning metabolic pathways are downregulated.  Since  
> insulin is the hormone for putting away sugar--either into glycogen  
> storage, or into cells for burning, or into fat stores--it is  
> constantly "working" in a high-carb environment.  And the result is  
> often insulin resistance, a kind of overuse syndrome.

That's interesting.  It suggests that diabetics are not necessarily  
better on a high-carb diet even when it restricts food to a short  
period every day (ie warrior-style high-carb) because they are still  
keeping their insulin levels higher than necessary.

There's only one other thing I'm curious about now.  From what I've  
read, fructose does not raise blood sugar, or need insulin to be used  
for energy.  I also believe it is easily converted into fat in the  
liver.  Is this the case?  If the above is true then presumably you  
can eat a lot of fruit and still return to ketosis quite happily  
after, without going through a glycogen-depleted state.



> This web site, though technical, does a good job of laying out the  
> basics in one place: http://www.zonehome.com/met/met.htm

Thanks I will read that, although it looks like I'll need to sit down  
and pay attention (which I'm not much good at doing in front of a  
computer...)

Cheers
Ashley