I bet you could lose that with the help of Mireille Guiliano's French Women don't get fat Leek Soup thing for a couple of days:
Magical Leek Soup (Broth)
Serves 1 for the weekend
Ingredients
2 pounds leeks
- Clean the leeks and rinse well to get rid of sand and soil. Cut off the ends of the dark green parts, leaving all the white parts plus a suggestion of pale green. (Reserve the extra greens for soup stock.)
- Put the leeks in a large pot and cover with water. Bring to a boil, reduce the heat, and simmer uncovered for 20 to 30 minutes. Pour off the liquid and reserve. Place the leeks in a bowl.
The juice is to be drunk (reheated or at room temperature to taste) every 2 to 3 hours, 1 cup at a time. For meals, or whenever hungry, have some of the leeks themselves, 1/2 cup at a time. Drizzle with a few drops of extra-virgin olive oil and lemon juice. Season sparingly with salt and pepper. Sprinkle with chopped parsley if you wish.
This will be your nourishment for both days, until Sunday dinner, when you can have a small piece of meat or fish (4 to 6 ounces -- don't lose that scale yet!), with 2 vegetables, steamed with a bit of butter or olive oil, and a piece of fruit.
Pretty extreme but so is 4-5lb in less than a week!
Good luck!