muscle protein & liver glycogen

[sungvimil]

Hi RRM, I have a question about basic metabolism.

Suppose that your liver depots are full of glycogen, and after some time blood sugar levels start to decrease. Hepatic glycogen will be broken down to stabilize blood sugar levels, right?

But what happens with muscle protein? It will only be broken down if hepatic depots are empty or it will happen every time blood sugar levels fall a little?

Thanks.

[RRM]

Suppose that your liver depots are full of glycogen, and after some time blood sugar levels start to decrease. Hepatic glycogen will be broken down to stabilize blood sugar levels, right?

Yes, liver glycogen can be reconverted into glucose to replenish the blood sugar level.

But what happens with muscle protein? It will only be broken down if hepatic depots are empty or it will happen every time blood sugar levels fall a little?

It cannot be reconverted into glucose.
It can and will only be used as energy for the muscles.
So that only liver-glycogen is spare glucose when it comes to keeping the blood glucose level at the right level.

[sungvimil]

RRM wrote:

It cannot be reconverted into glucose.
It can and will only be used as energy for the muscles.
So that only liver-glycogen is spare glucose when it comes to keeping the blood glucose level at the right level.

So muscle protein will be used only as an energy source for the muscles, but this will happen only if muscle glycogen depots are empty?

[Oscar]

Basically if your blood sugar is gone and the depots are empty, the body needs to find alternative energy resources, i.e. body fat and muscle protein.

[RRM]

Im sorry Sungvimil, i didnt read your original question well.
I read:

But what happens with muscle glycogen? It will only be broken down if hepatic depots are empty or it will happen every time blood sugar levels fall a little?

but you actually wrote:

But what happens with muscle protein? It will only be broken down if hepatic depots are empty or it will happen every time blood sugar levels fall a little?

Reading it right, my answer is:
There are hardly any black-and-white distinctions in the body. Most processes slide between moderate extremes. Constantly muscle protein is build and broken down, and some of that is utilized for energy, constantly. And that increases when blood sugar levels go down.
But when you are inactive, in general the body very effectively transforms hepatic glycogen into blood glucose, so that there is no increase in muscle turnover.
Once the liver-glycogen is gone, and the blood sugar inadequatley replenished through consuming food, much of your required energy will come from muscle protein.

[sungvimil]

Thanks RRM!

You wrote:

But when you are inactive, in general the body very effectively transforms hepatic glycogen into blood glucose, so that there is no increase in muscle turnover.
Once the liver-glycogen is gone, and the blood sugar inadequatley replenished through consuming food, much of your required energy will come from muscle protein.

How much it takes, on average, for the liver-glycogen reserves to empty?

If my liver still has glycogen from the previous meal, then I don´t need to eat so frequently for avoiding muscle-protein break-down, right?

Because of my job, I can´t eat so frequently like you recommend. I am doing a version of the diet but with bigger meals, without any problem regarding blood-sugar spikes, but I am concerned with muscle loss.

[RRM]

How much it takes, on average, for the liver-glycogen reserves to empty?

From full to empty: 400 kcal.

If my liver still has glycogen from the previous meal, then I don´t need to eat so frequently for avoiding muscle-protein break-down, right?

Technically thats true, but your liver glycogen will get depleted rapidly, and if you have to replenish your liver glycogen frequently, you will be frequently 'replenishing' your fat-depot as well.
Just try to take use as little liver glycogen as possible; so that its hardly ever empty (no muscle turnover) and so that you dont need to replenish it so frequently (less fat build up)

Because of my job, I can´t eat so frequently like you recommend.

Why not?
Cant you have a bottle (filled with juice) within reach at all times?

I am doing a version of the diet but with bigger meals, without any problem regarding blood-sugar spikes, but I am concerned with muscle loss.

The bigger the meals, the harder it is to get the balance between fat and muscle perfectly right. (thats (just) one of the reasons why bodybuilders always alternate 'fat and big' with 'ripped and smaller')