Safely, how long? Probably about 40 days on just water. It may be tough to get through the uncomfortable stages of experiencing the detoxing stages which can get quite low. It is crucial to be able to recognise this from actual starvation, which is indicating that it is essential that you eat for health and life. One thing also that you are doing besides losing all the built up excess weight and garbage stored in your body is *rehabilitating* your body to become closer to as it was when you were younger, or, before the years of being flooded with obscene amounts of insulin daily, and loads of other junk putting a load on your tissues, liver, heart and being. So when you acheive your first fast and than experience the ongoing results of feeling and being younger somehow, you may want to come back and write a rambling post like this one in response to a first timer. :)