If you're already active and in decent cardiovascular shape, then diet is the best thing. It really depends on your goals. I went from 265 to 205 in about 5 months and still looked like a pudgy fat kid after dropping 60lb's. Then I started lifting hard and lost another 25lbs but totally reshaped my physique. Now, I'm just trying to lean out like a mofo to hit 5% BF. if you just want to drop poundage, DIET is the only way to go. If you want to reshape your body, DIET/WEIGHTS/CARDIO is the only way.