Neither weight gain may have happened so quick for you, nor will the weight get lost so soon! Quick weight loss generally leads to weakness so it isn't even advisable. So go for a balanced diet with good amounts of salad in every meal and low cereal intake. Eat small meals every 3 hours, comprising mainly of light snacks like fruits, buttermilk, chana etc.
Next Steps
Add 45 minutes of walk to this to burn the existing fats to make proportion.
Health Tips
do not skip any meal as it may further reduce your capacity to burn fats naturally by the body