Hi !!!! You can lose 20 pounds in 2 weeks if you don't eat and you exercise excessively. But after you can regain the weight just how you lost it.But if you really have the will power to do that follow this diet:
Morning: 1 glass of water
Breakfast:Nothing
Lunch: 1 apple
Dinner:Nothing(But if you can't stand that eat 100g of lettuce)
Later if you know cardoons boil them throw them away except their water.Then anytime your tasty drink it instead of water it helps to lose weigth faster.
Exercise: Do at least 1 hour of running and 150 sit-ups. xoxo Good luck
Be Careful and later try to eat ssomething more than this cuz if you continue like this you'll become anorexic...