There are a whole heap of diets you could use to lose 20 pounds of weight. The question is; do you want to lose the weight permanently or are you happy to pile it back on again?
If permanent, long term weight loss is your goal, in my opinion there is no better diet than the one reviewed here - Strip That Fat Diet Review
The great thing about this diet is it compiles a daily food menu for you based on your food selection which helps you stick with it long term. It also isn't drastic like so many fad diets out there - you will be consistently losing 2lbs of fat (notice I say fat!) each and every week.
Click thru the link and check it out! Good luck!
Dan
How To Lose Weight Fast