Which is more important in weight loss - diet or exercise?
The science guys over at AsapSCIENCE explain it for you in three minutes.
I will add - since I do know several of the men of Chippendales - who know a thing or two about being in shape - that they put it at 80% nutrition, 20% exercise.
That's not to say exercise should be ignored. You burn more calories the more fit you are. And there is that endorphin high that's hard to beat... :)