I lost ~90lbs last year almost entirely by better eating / calorie reduction / diet alone. Twice when I hit plateaus (March, then in the autumn) I added minimal exercise back in. In the spring I used some of the 5BX stuff 5 days a week in the morning, so about 10 minutes. That lasted a month. In the fall I did it for a week (October?) but got distracted. I quickly tired of this, each time, and went back to diet alone.
At the end of the year I'd reached my weight goal.
 This year I've gone back to exercising. I did the January jumpstart fitness 'challenge' (some cardio, quite a few SparkPeople videos) and since then I've been working on pushups and squats, mainly.
 In short: you can do the weight-loss with diet alone. However, and this would be an argument for exercise with diet, especially strength training of some sort: when you lose weight, you lose fat and muscle. More fat than muscle when you have fat to lose, but you'll still lose muscle; exercise, especially some strength training, can help reduce that muscle loss. I now find myself in the position of having lose the fat I wanted, but wanting to put a little muscle back on.
 And if you're out of shape, the exercise is good for general fitness and cardio-vascular health. But that's different than your question.
"Habe nun, ach! Philosophie, Juristerei und Medizin, Und leider auch Theologie Durchaus studiert ..." (Goethe, "Faust")
| current weight: 212.0