Funnily enough Enduros are an endurance event.  Nutrition leading up to, during and after the event will have a big impact on your performance and recovery.  

Although every rider is unique, the three things every endurance athlete loses most of during an event are water, sodium and calories and these losses have the biggest impact on how a riders function and ultimately the end result.  Sure there are other minerals lost in sweat but they have a much lesser impact on your performance. - Darryl Griffiths - Sweat. Think. Go Faster.

By replacing the loss of water, sodium and calories during an event can assist you maintain peak performance and if you don't or do this poorly you will slow down a lot sooner.