I am not sure how much weight you will lose but I am pretty sure that unless you do this under medical supervision  you may lose some of your health. If you go on such a restrictive diet, you must have constant interaction with a medical professional to make sure you are not developing any nutritional problems or even problems like too low blood pressure or dizziness. You may lose a lot of muscle which eventually will reduce your metabolism . And one thing that you will not gain is an understanding of how to eat when you go off your diet. So it is quite likely that you will gain back your weight the way others, like Oprah did, when they went off very low calorie diets.