I've done quite a number of fasts in the past on water only. Most of them just short fasts of a day or two to but sometimes up to a week or more to clean my system out. The hardest part of water only fasting is the initial hunger that hits you in the first 48 hours. Using FAST weight loss I had no problems going three days and could have comfortably done another 24 to 48 hours. Not sure what you have put in the FAST formula that takes the hunger away but the results are brilliant. The first three days saw me lose over 4 kilos. I did a second FAST two weeks later and lost another 3 kilos. The weight has never come back on so the product really does do what is claimed. I'm a stone lighter in the old scale (14lb plus) and feel so much better for it. Using FAST is going to be a regular occurrence for me from now on. Highly recommended!