How much weight can be lost with diet alone?

F29 347lb 5"9'. I've been dieting for a couple weeks and I've lost 10 lbs. I'm an all or nothing kind of person, and I always have been... in the past, I've gone hard on dieting and exercise, then eventually I would burn out and give up and go right back to an unhealthy lifestyle. But I'm really trying hard to be consistent with my diet, and I'm doing really well so far. I know I need to add in exercise too, but I'm afraid I'll get overwhelmed again and slip back into old habits, so I'm really just focusing on the diet for now. I'm doing 1700 cal a day, protein, veggies and fiber, all of that good stuff. I know eventually I will need to work exercise in, but just for right now, is it realistic for me to expect weight loss while being relatively sedentary? Does anyone have experience with this?