How much is diet and how much is the band...

I'd say both are fairly equal...example: The band helps you eat much much less, BUT, you have to make the right choices of the right foods such as solid proteins, veggies, etc.  I know that if I don't think about what I'm eating and plan my meals, I'll eat junk.  I can eat a heck of a larger portion of junk food (chips, candy, cookies, ice cream, pizza, tacos etc) compared to my 1 cup of solid protein and veggies.  And then I'm not even satisfied, then all I want is junk food.  So we do have to worry about types of food we eat, so it is still a "diet" because you can't eat anything you want for every meal.