How do I lose 15 IBS in a month? I don't mind hunger

Go slow. Reducing intake of food will cause weight reduction. Loss of 15 lbs of fat in a month means burning off 4500 calories every two days, without taking in any. Essentially you will have to go without food for a month. This would not be healthy and in-fact would be dangerous. You should aim for a slower pace for the sake of your health.