Before when I used to lose that much I'd do it the unhealthy way (big calorie restrictions) and lose it within one week. I'd reduce my calories to under 900 calories and be miserable. Most of it was just water weight and not fat. Now that I've started 1200-1300 calories and have been exercising I can lose that same amount of weight and be healthy and happy at the same time. I thought that would not work for me but I surprised myself. 
You Rock!