Camebridge diet is a food replacement diet I am on step 2 which allows me to have 3 of their products a day + a balanced meal I consume roughly 6-700 calories a day + 2.2L of water. It cuts out all Carbohydrates fats sugars and acids. Apart from those in the products and allowances in the daily meal, it forces your body to enter Ketosis which is how it gets its quick results.
However it is not a easy diet and requires a will of iron.
I have been writing a diary to help people understand what it’s like, (look for dairy of a saxman). I did this diet about 8 years ago and lost 5 stone in 6 months but now am back on it because life happened.