I am one of those people who cannot run on an empty stomach but obviously not on a full one either. Depending on how hungry I am and how far I want to go I will toast a bagel or two before a run and set off within half an hour or so. And I recently discovered that if I have an energy gel (experimenting before the marathon - see I do read the manuals!) I tend to run pretty well. Well, better than my usual slow plod.