I usually drink a muscle milk shake before I leave (which I am about to do actually), and that seems to be enough food for a while. However... the first 5-10 miles still sucks. My cruising speed takes a while to get to my normal, which I think contributes to feeling bad in the beginning, because I feel so slow. I have found that looking down less at my speed seems to help a bit, and I can feel when my body hits its groove. Then I don't notice how slow I am, and feel a little better.