Dear friend share your details such as, daily activity and your diet pattern based on that only i can suggest you something . one thing always keep in mind diet does not mean to have boiled food tasteless food or eating soups and salad . it should be combination of each food group.

Hello! Now problem starts from the word "quickly" which is not at all possible. When we can't gain weight in 1-2 month then how is it possible to lose all by 2-3 weeks. You need to follow a balance diet plan given by a qualified dietician with 30 min of activity. By this one can lose 1-3 kg weight per month, which is normal n good for health. Wish you good health.