[rhinoceraptor]

> I can run much farther if I ate my previous meal than if I didn't

If anything I would think the reverse to be true. Runners and cyclists eat sugar gels instead of 'real food' because gels are easier to digest, and all the energy you spend on digestion isn't spent on the activity.

[paulddraper]

They generally only do that during activities or shortly (30-60 minutes) before. Gels are eaten rather than "real" foods to match the glycemic index to the rate of energy expenditure.

In any case, this really only applies to lengthy activities, where glycogen is exhausted. It doesn't matter for a 5k or even a 10k run.