I had a discussion with someone - wait, it was raffo - about not wanting to rely on exercise to lose weight. If it's added on later, that's fine (or in flexibility exercises now, that's fine), but it's nice to be able to lose weight comfortably.
When I was younger and lived near a park (probably said this already), I would bike and run a lot. I'd get a bit anxious when I'd have knee or shin problems from too much running (never had anything that prevented biking, I guess) - and my eating just matched the exercise and I didn't lose weight. Something has change as I've gotten older, though, and I don't have a jones for the junk food - previously, that would start to make a comeback around a month.
That said, I know there are other people who consume less once they're exercising - I'm just not one of them - it causes ravenous hunger. though it does provide a way to run off frustrations.
Starting at about 55 pounds over, though, I don't want to exercise and get banged up (I would get banged up at 160 pounds). Exercise makes me impatient to see results, too. Doing nothing doesn't so much.