^word.. it's hard. very hard.
also, if you are trying to drop fat quick, the best cardio believe it or not is not your typical 45 minute run at 6 mph or whatever.. but rather HIIT, or high intensity interval training.
a good quick 15 minutes, and you burn off much more fat, while minimizing muscle loss.
i usually do a 5 min warmup on the treadmill at 6 mph, then 1 minute at 10, 1 minute at 7, 10 minute again at 10, back to 7, etc..
another good one is called 30's, where you sprint for 30 seconds, jog for 30 seconds, and continued for 12-15 minutes.