I don't agree with fasting and this person pretty much summed up why on "The Vegan Forum". I couldn't have said it better myself.
[b][i]I need to add my 2 cents here. I don't believe in fasting or "detoxing" (unless it's a detox from drugs or alcohol) and will explain my reasons.
When you fast your body does not stop requiring protein. Your fat may be broken down into fuel but amino acids (the building blocks of protein) will come from the breakdown of muscle. That may be the muscle of your limbs, trunk or heart.
Yes, some muscle will be lost. But not from the heart (unless you go right up to the point where you have no fat left (starvation)). Studies have been conducted on what percentage of mass is lost from each of the body's systems. The heart does not lose anything. This is within Shelton's book.
This loss of muscle mass will result in a slowing of your metabolism. Therefore, unless you spend weeks to months regaining the muscle mass you lost on your fast, or you readjust your future caloric intake, you will most likely regain any weight you lost on the fast.
Fasting shouldn't be done with the goal of permanent weight loss in mind. As I said I expect to gain weight. I know from past experience that muscle comes back very quick.
Regarding detox, if you are not eating toxic foods then I assume you are trying to get rid of the toxins in your fat stores.
There are benefits beyond detox. Energy spent on digestion can instead be used on healing. Also studies now are finding periodic fasting can have the same effects as calorie restriction which increases the length of life. Personally I'm not really interested in "detoxing".
Your liver (and to some extent your kidneys and lungs) is the main detoxifying organ in your body. That is the #1 job of the liver. I would not think of stressing my liver by releasing the toxins in my fat stores in great amounts (ie, by fasting).
Covered by Shelton. Simply the evidence shows that this isn't a problem.
Since you cannot pick which fat cells will shrink (the toxic fat cell vs. the healthy fat cell) and a zero % fat count = death, it appears that you cannot detox your body past a healthy fat ratio.
OK, detox isn't the goal anyway. But it would appear if it was, that you would still be improving matters...? But really I couldn't care less about "detoxing".
Please remember that your body does not stop requiring vitamins and minerals during a fast. What you are feeding yourself during a fast is your own "toxic" fat and your much needed muscle mass. Why anyone would want to do this to their body is beyond me.
Covered by Shelton. Studies have been done showing that (excuse me vegan world) animals fed food that had the nutrients removed died in less than half the time of animals that were simply starved to death.
Furthermore, what it comes down to, is people have been doing this for centuries and the evidence shows that it isn't actually bad for you. Still modern science would never dare advocate it, etc, as they wouldn't want to get sued, just in case someone did die. And of course fasting doesn't make you immortal.
The average person can go more than 50 days on fasting. Some people have gone over a hundred. I'm not planning on anything like that.