Protein in terms of calories vs muscle repair

[Nstart]

This is a question I've had a while but I have never been able to find the answer to it.

We all know that 1 gram of protein is equal to 4 calories. Now, when we consume protein, does the body use that protein first to repair and rebuild muscles or does it use it as energy first, and then if there is any left over, it uses that protein to repair muscles?

Lets say (in a theoretical world) I wake up after 10 hours of sleep. The previous night I burned all the food I ate running a marathon and I did not eat before I went to bed. When I wake up and eat 2 pieces of chicken with 60 grams of protein, does my body first use the protein I consume to replenish the bodies energy supply, or does it first use the protein I consumed to repair and rebuild muscle and then use the extra as energy?

[C_Bino]

First what you need to understand is that protein is not only used to repair muscles. Its used to generate tissues; hair, skin fingernails, organs etc etc. It is needed for bones and almost EVERY aspect of your body, muscle repair is not its first priority. And energy is certainly its LAST. Your body can use amino acids when needed as a supply of energy but that would be in dire cases where you are starving yourself of other macronutrients.

[im83931]

The circumstance you described is very unique anyway. When running a marathon you will burn protein for fuel. You will also use most if not all of your glycogen. You will be depleted for a few days. I am not sure your experience in running or how many marathons you have completed but all of these would be factors in your question. An efficient runner burns 100-120 calories per mile. By mile 18 you will start to use protien as your energy source unless you (a) are very experienced and efficient and (b) eat while you run.

[Nstart]

Thanks guys.

I don't run marathons. I was only using it as an example to show my point in an extreme manner. C_Bino gave me exactly the answer I was looking for.