Working out does something, but working out will only burn a fractional amount of calories. Pure cardio will burn a decent chunck of calories but burns almost none afterwards. Weight lifting burns a few calories for about an hour of lifting, and burns some aftewards to assist in muscle recovery, but doesn't really have a very significant effect.
Diet is the only real way to lose fat. To put dieting into simple terms:
x - y >/= 1100
x being the number of calories you ingest daily.
y being the number of calories you burn daily.
1100 being the average for subsistance (necessary for bodily fuction) calories in a human being.
On top of the general concept of burning more than you eat, there's the concept of motabolization. To keep your motabolism up you have to eat at the most once every 2-3 hours at the longest. In this way your body is constantly functioning and burning calories.
Sig courtesy of that photo-matic magician limba
I went out the way that I fight. I went out on my shield. That’s it. Done. --Chuck Liddell
My goal is to end my opponent --Carlos Condit