5 pounds is too much to lose in one week. Safe weight loss is considered to be 1-2 pounds/week.
Since a pound consists of 3500 calories, you'd have to burn 17,500 calories in order to lose 5 pounds. And don't forget that you also have to eat during the week, which means you'll also be taking in calories.
you can't take in more than 1,000, that is all. walk, walk, walk drink plenty of water,