I'd go slow on fasting.
Seriously, unless a person is following a colon cleanse program, fasting does not help you dieting or losing weight. If you're working with a nurse or doctor, medical person or some dietary expert, longer term fasting should be done with extreme caution. Fasting for a day is not too risky.
Longer than that, you'd need a very good reason to be doing this fast (liver cleanse...vegetable juice fast and/or nutritional supplements), a special dietary protocol and very restricted range of activities.
Be aware that when you fast ..let's say for day ... your metabolism slows down. When it slows down, it significant lowers your chances of losing any weight. In fact, after the fast and return to normal eating, you'll put the weight right back on.