I understand your concern. Physical activity n diet will help you to keep fit n healthy. Have small n frequent meal through the day. Cut down portions of cereals. Have protein rich foods like dal, rajma, chana, sprouts, if non veg then eggs, fish or lean meat. Have nuts n fruits to keep a balanced meal.

First and foremost you must understand losing your weight is a very gradual process. You should have strong determination and patience if you want to lose weight. And it cannot happen suddenly. Losing too mich suddenly is also not good for health. You have to follow a strict diet and exercise schedule. Regarding diet - have small multiple meals instead of 3 big meals, eat food rich in proteins and fibres like egg white boiled chicken vegetables fruits pulses, avoid carbohydrate rich foods like rice curds oily foods sweets ghee and other junk food. Regarding exercises - start slowly with brisk walking, then change over to jogging, running and other abdominal exercises. Never over strain yourself. And always keep yourself well hydrated and enjoy whatever you do...consult dietitian they will do the needful.