I've lost that much in two weeks when I was on a soft food diet because of me wisdom teeth operation. Nothing but hot wheat cereal for two weeks straight. Also when you flush the system say accidentally by drinking old juice or something like that you can loose that much in a week. But both of those choices are not a healthy way to do it. If you count the calories and use a calorie counter like www.myfitnesspal.com
it will help you eat healthy and loose weight.