Not that this is any thing really new, but I DEFINITELY see a change in my metabolism when I use weights and resistance training. Once I get some muscle on me, I find I can eat more (not an excuse to eat a ton tho!) and the fat comes off. Cardio is great and necessary but it is important to get resistance training in there too. And no ladies, you will not bulk up.
Don't half ass your workouts either. Really get your sweat on! (Assuming you are in good health of course!)