My friend went on a 5 day water fast and lost 12 pounds. Well she is small to begin with, and I didn't see the point.
But my question is it at all healthy? I mean, would to actually be ok to do it then start your diet, sort of a detox program???

I'm not sure a person needs to "detox" your body is basically self cleaning if you drink enough water and get enough fiber.

Going on a 5 day water fast you'd lose some weight, but once you started eating again, it's not going to stay off.

The question is how much water did she drink? If she drank an abundance of it then a good majority of the 12lbs could have been water weight that her body decided it didn't need since it was getting so much water. It would have to be considering "she is small to begin with". I started dieting 8 days ago and for the first week I ate 1000 calories per day and rode a stationary bike at 16mph for one hour everyday. According to several calculators I used, this would bring me a 3400 calorie deficit per day or 6.8lb a week.

Stepping on the scale after 7 days however it showed I lost 9lbs though some of that is in fact water weight. Did I mention I weighed 302lbs? So if I did what your friend did at my weight and had a 4400 deficit that's about 6lbs in 5 days and assuming your friend "is small to begin with" I'm assuming she weighs much less than I. So simply put I'm guessing a lot of that 12lbs was just water if I would only lose about 6 at my weight and exercising everyday.

I don't think it is healthy. If your friend only drink water without eating meals, it means his body is lack of energies that foods can provide. Just be patience, it is the only key to your diet success.

There are plenty of liquid detox diets that you can find free on the web. Only water would lack certian nutrients. Weightloss is alomost always water and waste matter-which is very good to get rid of. Death starts in the colon. Some people have 25lbs+ of waste (poop) in them. If you aren't going to the bathroom 2-3hrs after every meal (not very many people do) then you are "backed up" and are carrying excess waste matter that you shouldn't.