Hi Nirmala,
Only loosing calories wont work for weight loss. One pound of fat (0.5 kg) consist of 3500 calories. So if you want to loose weight then we need to put a deficit of so much of calories. So more we eat calories, more we need to exercise. Cardio exercises are the one of the best exercises to burn calories and thus reduce body fat percentage. Cardio exercises includes swimming, skipping, jogging, brisk walking ,etc. We need to do these exercises atleast for some 45 min, 5/week for better results. So, if you want to loose weight by burning more of the calories then cardio exercises should be your first choice .Most peoples thinks that doing more cardio for 2 hours will help burning more calories but it will also lead to muscle loss so we need to do also include resistance training exercises so as to restore and maintain the muscle mass. Cardio done for 1 hour is really enough to burn calories but if you want to do more, its must for you to also include some more of resistance training exercises too. Resistance training exercises are like push ups, lunges,squats, etc. We need to do these exercises for atleast 30 min, 3/week. This type of exercise plan will help to reduce calories.