Your body uses energy to digest food. For short rides, if you eat just before the ride, you will be wasting energy digesting it, only to get the energy from that food towards the end of your ride, or even after it. I wouldn't say ride on an almost empty stomach, because the end of that hour or two you will be completely empty. But I wouldn't bother eating less than 2 hours before a ride, rather stick to your regular eating schedule and make sure it includes a decent balance of protein, potassium, and carbs. For reference, you burn carbs about a day later, while protein is a few hours later, and sugar is used almost immediately. That's why you want things like fruit while you're riding, to burn it's quick acting fuel.

By the way, I read that Powerbars are so full of artificial crap that they about 1 1/2 hours to digest. So don't bother with those kinds of things unless you're doing a 3 hour ride.