Exercise.
As in: eat what you want, just go jogging/ running before breakfast every other morning, and fiddle about with some weights as well to build up muscle, which in turn burn calories while you're doing nothing.
Result? You'll lose weight, gain muscle, and have no impact on your diet ^^
May as well just be me though, I've got an extraordinarily high metabolism (meaning I lose weight fast, but I gain it much faster too).