Because one is not ingesting fats when fasting the system produces little bile thus not flushing the gall baldder as when ingesting fats. This >>MAY<< create conditions that >>>>MAY<<<< be favorable for the formation of stones. It is not a sure thing. It is just a >>>precautionary <<< measure. Waddya think that the millions of people who fast each year with amazing results are suicidial?????????? Use common sense. Loose the fear and do some research. Thererare several ways to do liver flushes. Research them. You will find plenty of help in the liver flush forum. The most common is the Hulda Clark protocol.