Cut down on processed carbs and you'll start noticing a difference (this is from a rower and nutrition's one of the only things I'm any good on!). Do still eat carbs or you won't be able to keep up with your exercise, just shy away from pasta etc and aim for more beans and pulses. You can't spot reduce fat, so there's little point doing crunches etc now. Most people get definition if they lose weight sensibly without the need for stuff like that. If you want to look good as well as just lose weight, lifting weights will help. Doesn't need to be anything heavy, but free weight exercises with just a bar will do you no end of good - muscle's an active tissue so just be existing it burns calories. Keep track of your calories, if you're really committed then I'd recommend Fitday (it's free) - you'd be amazed how wrong your judgement of what you've eaten can be! I used it the other way round, to put on the right kind of weight without putting on fat, but I've known people use it just as well going the other way (which is what it was originally built for). Sensible calorie deficit, sensible eating, cardio and weights (if you want to, not completely necessary) should get you looking awesome.