Can I lose 100 pounds in 60 week?

I'm a 20 year old woman, 5'4, and about 270 pounds. I want to lose weight so I get down to 170 pounds. I plan on doing this by exercising 4 times a week. 2 days a week on the treadmill, and 2 days a week lifting dumbbells. Every 2 weeks I will make both workouts a little more strenuous until I'm at the pace that I want to be at. I also plan on losing weight by eating right. When I say "right" I mean in portions. I'm not going to deprive myself of certain foods, because I know that I will end up crashing and end up binge eating if I do. I'm going to be careful of what I eat, but treat myself every now and then, as long as it is in portions. If I do this, could I reach my goal in 60 weeks? Is losing 100 pounds in 60 weeks realistic? Safe? Healthy?