I don't know whether you're asking this question for yourself or for your child, but either way - the results will be scary. Okay, let's get to the facts straight - if you try and lose weight in a rapid manner, you'll gain more weight in an equally rapid manner after some short term success. If your child is obese, you should first regulate a proper diet that has all the essential nutrients and vitamins. Cut out all fatty foods from your child's diet and stop pampering your child with junk food. Ensure that your kid gets a lot of exercise and encourage your child to play regularly (not Xbox - outside!).