[s]Because politics will only get me fucking nowhere and people without self awareness to lob judgement at me.[/s] I will briefly pop my head in to point out, it's pretty obvious food intake is the most important to gaining and losing weight. Exercise is good for your muscles and bone health. You want to do both, if you want to diet and lose weight effectively. It's not healthy to not exercise, even if you're weight is fine. Not just because of weight. But all that matters is how many calories you take in and how many you burn off. In fact, some exercise, like weight lifting and such. Will make you -gain weight- just from muscle mass. 

Source: Person that's doing that and has lost about 60 pounds in about six months. (40 in the first two from extreme ends with both. :D)

[i]So now that I've responded in something I actually care about and can't be bitched at, I'll be back in my bunker.[/i]