Short answer: No, you're just going to make it run badly and/or quit on you.
Longer answer: Engine RPM is regulated by controlling the amount of air and fuel that goes into the engine cylinders. Airflow is regulated by a butterfly valve, when you twist the throttle or push down on the accelerator pedal you are opening that valve either directly through a mechanical linkage or the engine computer does it for you. Opening the throttle lets more air through - more air and fuel, more bangs, more RPM. Rolling off the throttle closes the valve and you get less air, less RPM.
So airflow is already being regulated, if you restrict that airflow yourself then you'll starve your engine of air at higher revs, making the air/fuel mix too rich which will ruin performance, maybe cause it to quit altogether and lower your mileage.
If you want to reduce your fuel consumption then the best thing you can do is be less aggressive on the throttle - stop caning it and you'll use less go-juice. Also, make sure the bike is well maintained and tuned well.