Originally Posted by hamster

I don't think it depends on physiology and conditioning, but simply on your objectives. Eating on the bike helps you go further _right_now_, on this specific day. Not eating helps you to be able to go further in general. I'm not an ultra endurance rider but I just pulled off a pretty tough long distance event (you may have seen it in SoCal subforum) and my longest ride in 2 months prior to this event was 60 miles. I was training strictly on water. Of course, on the day of the actual event, it was, just like Machka says, 200-250 kcal/hour religiously starting 30 minutes into the ride.