Question about glycogen stores
 

So once you eat carbs and fuel your glycogen stores, if you go carb-free and don't do any intense exercise, how long do they last before depleting? In other words do you use any of your glycogen for every day activities like walking and doing chores around the house or even sleeping?

Basically, at 20 net carbs, you should be depleted in less than 2 weeks ie the induction phase. Most likely less than that time. You body is also going through some other changes during that two weeks.

Physiologically speaking, the body uses the glycogen reserves as a buffer for sugar depletion. It helps keep your sugar levels even between meals and also is closer to the muscles.

Your body uses glucose/sugar internally. It is the preferred energy source. Glycogen is a glucose polymer. It is the easiest and fastest to convert into sugar.

It usually takes people a couple of days to see ketones in their urine, which would indicate they're burning fat instead of glucose.

So if I get to that point and continue to eat between say 20-50g of carbs per day, does that mean if I go run for like 5-10 miles I will hit the wall and bonk (previously it might've taken me 16-20 miles while carb-loaded on a high carb diet)? Or is it that adapting to the low-carb diet prevents that because my body better knows how to burn the fat?

Adapting to low carb diet means your body will burn fat primarily for energy, but will also provide glucose needs by converting protein to glucose via gluconeogenesis. Obviously if doing long distance running, you need to ensure your body is fueled, so if not fueling with carbs, then you need to take in enough protein to provide the glucose requirements for the run, and for muscle repair, otherwise you'll hit the wall anyway.

Lee

Yeah protein intake is not an issue. As far as my taste preferences, I would much prefer a high protein food than a high fat food. If anthing I was worrying about taking in too much protein and having 58% of it turn into glucose (based on some misleading information I read on the web).

That is a interesting question on what the body is converting to glucose.

I believe that the human body

• while on LC diet has normal blood glucose level
• can generate glucose via glyconeogensis
• stores glucose into fatty acids/fat
• while on LC diet is metabolizing fat/fatty acids
• can survive on a fat only diet

There is known pathways for converting protein into the starting material for glyconeogensis. So that could be the glucose source.


The question is that has not been addressed is fat being converted into sugar. It seems strange to store glucose into fat and not have a mechanism to retrieving the glucose.

There is no known metabolic pathway for converting fat into sugar in most animals. Not known does not mean there is none or that it has been ruled out as never happening.

In protozoa (single celled organisms) and plants, there are glycosomes, a membrane-enclosed organelle that contains the glycolytic enzymes. The glyoxylatic enzymes can convert the products of fat catabolism into the starting materials for glyconeogensis.

There are similar structures in the liver called Peroxisomes. They are present in all animals. Their numbers appear to increase when someone is on a LC diet.

The end point of fat metabolism is acetyl-CoA. This happens inside the mitochondria. There is a funky mechanism in the mitochondria wall for moving malate in/out of the mitochondria, the malate-aspartate shuttle (sometimes also the malate shuttle). It has been given the assignment as a biochemical system for translocating electrons produced. Malate is converted to oxaloacetate which is used as the starting material for glyconeogensis. Although this mechanism does exchange energy, it is interesting that it is cyclic. It goes both into and out of the mitochondria.

What is missing is the enzymes for changing acetyl-CoA into malate or the glyoxylate cycle. There is some (inconclusive) evidence that these structures could have glycolytic activity.

If this was true, it might explain a lot about the relative success of ketotic/LC diets.









P