How do you Lose 20kgs in a month?

Eating Plan, exercise and and a positive attitude.

You should be running off a 1200 calorie per day diet and with 45 mins to 60 mins of good solid exercise you will be well on your way.

Simple things like drinking water instead of soda and fruit juices makes a massive difference, no more "fast food", eating low carbs, high protein meals, and eating 6 times a day (smaller meals but more often).

Set a start and an end date, also allow yourself one "cheat day" this will stop you binge eating and cravings. I don't mean eat 12 Pizza's on that day, but allow yourself those "fun" things, like a soda and a hamburger.

Also keep a weight diary, weight yourself every Friday and have your cheat day on a Saturday (when you go out with friends and such)

Good Luck - and remember "think thin"!