My wife bought me "Eat & Run" by Scott Jurek last week as a Valentine's day gift and to help me fill a train journey over the weekend. The ghost writer did a good job. It's a gripping read, especially for a longstanding vegan. The broad categorization of diet is however all Scott and I have in common. Most importantly he started training and developing physical and mental strength whilst a senior school student. At that age I was an active walker and badminton player but those pastimes aren't in the same league as an ultramarathon.
Nonetheless there is an element of "I could do that", which at the moment I couldn't!