I had the same problem too, though my intent was not to loose weight. ~3 months of cycling; 30"->28" waist and 10 lbs lighter. I have to admit I did initially change diet for health, but now I need a steady dose of In-n-Out burgers to avoid turning into a pole.

If you want to get new belts or poke more holes in them, do it quick. I've already lost a few pants where the leg opening are all frayed. Too bad they're khakis and not jeans, so the fraying isn't in style.