i dont think its impossible, a little bit unhealthy, but im in the same boat id also like to lose 20kg in a short amount of time. If you really put your mind to it, get 30 mins excercise every day if not twice a day by going on a brisk walk or something, and stick to mainly fresh fruit and veg. no fruit juices, alcohol or any other clearly fatty products, even reduce cheese

. and if you have to drink, vodkas the best for notputting on alcohol weight.

i really wish you luck because im on the saem kind of program trying to lose excess weight before my bday in three weeks

. let me know how you go!