I need to eat around 3000 calories per day to support my powerlifting training, and if I don't eat something first thing in the morning with a shitload of carbs -- usually something like rolled oats, berries, and a few bananas -- then I'm usually gassed and feeling like crap by 10.
A few friends of mine fast intermittently and train in the morning before eating but it's beyond me how that is not just pure torture.