It seems that human evolution has primed us more for hunting in order to eat, instead of eating in order to hunt.
On Thursdays, my gym day and my Krav Maga day overlap. I have breakfast at 7, work out from 1:30 to about 2:15, then do an intense session of Krav Maga from 7:30 to 8:30. I am never lacking for energy and get through Krav with energy to spare, then finally eat at 9 pm. Saturdays I go to Krav having fasted for about 18 hours.
Has anyone considered the possibility that "fueling up," while providing some energy, creates a very large placebo effect? That is, subconsciously thinking, "I have eaten recently, therefore I have the energy to push myself, therefore I will give it all I've got" vs. thinking, "I haven't eaten. How will I have energy? If I go too hard I could pass out and damage my body. I better take it easy" and hitting a self-imposed wall. Food for thought, I guess.
You lousy kids! Get off my savannah!