It can, but exercise, along with it, will help you lose faster and it will keep muscles toned and help eliminate lose skin.
Yes. In my experience, exercise is mostly helpful for toning up and staying in shape, among other things, but is not necessary to keep a healthy weight. Diet is the number one factor.
Yes. I've lost 30 pounds and kept it off by changing my eating habits without exercising. I'm not saying exercise isn't good, but you can do a lot with diet alone. I've had problems with an ankle and haven't been able to exercise. I'm hoping that I will be able to exercise in the future and that it will help me lose more. I have another 20 that I need to lose, and I'm at a plateau right now. But I know it was diet that enabled me to lose this first 30, because I did not exercise at all.