Never start any diet program before consulting with your Doctor
If you want to lose 4 kg in a week it will definitely come back. Your weight will just go up and down forever. The best way to lose weight is just to eat healthy, drink a lot of water and work out. For a lasting result you should lift weights, don't eat junkfood, snacks, but just eat healtier, for example fruit, vegetables, eggs low fat quark etc. Good luck.