A few people have raised the issue of the bonk (fatigue resulting from muscle glycogen depletion - usually a couple of hours in) during extended periods of strenuous exercise (usually cycling). They would normally hit the Gatorade or some other high sugar concoction at this point and want to know what to do in a fructose free world.
The answer is that this is the one and only exception to the rule against ingesting fructose. Fructose is an extraordinarily efficient means of refilling depleted gycogen stores for those pursuing high endurance athletics, its just that for the rest of us (who generally have glycogen stores full to overflowing) all that fructose goes straight to fat.
So I would suggest that an athlete experiencing the bonk should use fructose flavoured drinks during the event (for the fastest glycogen replenishment) but should revert to glucose drinks and normal (non-sugar) food afterwards (and just like the rest of us) avoid fructose the rest of the time.
Cheers
David