I want to start some basic dumbbell training in the mornings, but I am sooo cranky in the morning without my breakfast first! But the guide says not to eat before exercising. Is there an important medical reason for this, or is it just likely to be a bit uncomfortable to exercise on a full stomach? Is it ok to eat something small first, e.g. a banana? Or will my body simply adjust to the routine after a few miserable days working out on empty?