Why? Do you have a wedding to attend to? I'm sorry to disappoint you but that is next to impossible. Losing weight is hard as it is and it is simply not possible to do it within a single week. It takes many months and hours of dedicated effort to reduce even a few kilos. Even with a strict diet plan and constant exercise you will not be able to lose weight within one week? Even if you go on a crash diet, you might not be able to do it and besides this does more harm than good, so pls don't try it.