That is not the best of plans. Cardio on an empty stomach actually leads to a decrease in overall intensity. So it may be true that more fat is burned on an empty stomach - although it isn't much more - more calories are burned on when not in a fasted state. Furthermore the effects on metabolism throughout the day are supposed to be greater because of the increased intensity and calories burned. This allows you to continue to burn more calories throughout the day.
It's the same theory as lifting. Yes you are breaking down the muscle when lifting, but the growth comes from repair. So yeah you might burn more "fat" doing cardio on an empty stomach, the total calories burned are greater throughout the day when having something to eat first. The total effect is greater this way.
Plus, it lessens the chance that the body turns to muscle for fuel.