Calories and the marathon

Over the past few years, I have made an effort to get at the heart of some of the finer details of marathon running. Training always can take you a long way, but from a physiological standpoint, we simply have a hard time making it the full distance feeling strong. The calories we take in (or lack of) during the race make a huge difference in our performance. Here a quick video I made regarding part of this complicated discussion: http://youtu.be/NUKekOgLROQ