Additionally excess protein can be converted to glucose and there is some level of glycogen stored in muscle meat. (vespapower.com)
The frequency and intensity of your training leads me to believe that you are running with rather depleted muscle glycogen stores on a regular basis. (drrosedale.tenderapp.com)
Most of it must be water loss, lowered intestinal content, and perhaps lowered stores of glycogen in muscle and liver. (advancedmediterranean.com)