Carbohydrate management is essential to avoiding bonking in endurance events.
http://www.mensjournal.com/health-fitness/nutrition/paleos-latest-converts-20130618
"5. Since oxaloacetate is depleted by gluconeogenesis, Dr. Atkins has postulated that fat calories wont be utilized in
the absence of carbohydrate. Based on what you now know about the citric acid cycl
e, what is the basic falacy of this hypothesis? (Where does oxaloacetate come from when we break down protein?) "
http://www.med.unc.edu/neurology/files/documents/child-teaching-pdf/CITRIC%20ACID%20CYCLE.pdf