They say that you can't out-run a poor diet and that is (for the most part) true. Intake is more important to weight loss than output - as has been mentioned, if you exercise more, your body will tell you to eat more, so you need to pay attention to intake. That said, I've gone through stretches where I'd average 4000+ calories burned per day, and I just couldn't stomach consuming the calories necessary to maintain weight (I wanted to continue to drop weight, anyway).