Fasting is simply not eating. Some people go on juice fasts (only drinking juice), one day cleansing fasts, longer religious fasts, etc... In general, I do not think fasting is an effective weight loss tool. Most of what you lose is water and fasting does not "cleanse" your body as it claims to do.
Fasting for "2 weeks at a time because you are committed to its results" is verrrryyy dangerous, tsmith. And not to mention a waste of time!
I agree that fasting can be great. The BEST reason to do it is religious/spiritual, IMHO. Medical reasons are also legitimate (I have GI track issues and benefit greatly from a day or two fast every now and then, as needed). Weight loss and/or a new outlook/relationship with food can be a wonderful side-benefit from some . . . but I don't think that ought to be the primary objective.
But, as always, never say never and never say every . . . if someone really feels guided to fast over a longer period, I wouldn't argue with them (unless they are doing it for the second time . . . or third or fourth).
I fasted for 1 week and 2 days...I lost 13 lbs. I was taking mutivitamins during this, & drinking lots of water. I also have not gained any of the weight back. If you are prone to eating disorders, or have had one at all, I HIGHLY, would NOT recommend fasting at all! I do recommend doing your homework before you do anything like this. If you fast for too long, you can do major damage to your body, and not realize until it's too late. Different things, work for different people, in different ways. Be careful, do your research, and God Bless.