I also thought that the wall, particularly common with marathon runners, was a symptom of running out of sugars.

With long distance running, the “common knowledge” is that you drink electrolytes (which are mixed with sugar) and eat some sugary gels to replenish energy. 

I reject that approach and use LMNT raw for electrolytes but I have not found yet a good replacement for sugary gels to get some more energy during the race. 

For sure I don’t stuff myself with carbs the night before a race. I run in a fasted state except for the gels that I will take during the race.