Is fasting healthy?

Question

My friend said that if you fast for say two weeks or thirty days, it will really improve the health of your body. He said it includes the flushing out the toxins in your fat of the body, improving the senses, increasing immune system, etc.

First, I had to define fasting:

According to Registered Dietitian Gail Sommerfeld of Loyola University and Peter Vash, M.D., Medical Director of Lindora (Calif.) Medical Clinic and past president of the American Society of Bariatric Physicians, a fast means no food whatsoever and no liquid except water. And if it is for less than 24 hours it isn't a fast, it's skipped meals.

I looked fasting up:

According to The Prescription for Nutritional Healing, Fourth Edition:

“Fasting is recommended for any illness, as it gives the body the rest it needs to recover. Acute illnesses, colon disorders, allergies, and respiratory diseases are most responsive to fasting, while chronic degenerative diseases are least responsive. By relieving the body of the work of digesting foods, fasting permits the system to rid itself of toxins while

As well as this:

Fasting and Weight Loss

If you weed through all the controversy, you'll find that most medical experts agree on one thing: fasting is not a healthy weight loss tool

So, is fasting really healthy, as my friend said it is, or is there medical evidence disproving it?

Answer 1

Your friend suggests fasting is a way of flushing toxins. This indicates an assumption that: a) your body is full of toxins, and b) flushing them would be beneficial.

This reminded me of a skeptoid episode which addresses the detoxification myth, in all its forms: http://skeptoid.com/episodes/4083 ... though I don't know that fasting is specifically called out.

Your second citation starts with "Fasting is recommended for any illness"... it should be immediately obvious that this source is pseudo-scientific "woo" and should pretty much be ignored.

Your 3rd citation seems the most on the money. Except for some very specific circumstances (colon issues maybe, pre-surgery obviously) fasting is not a valid treatment for anything, and doesn't lead to sustained weight loss

Answer 2

Some people argue that doctors aren't taught about fasting because they're not taught about diet.

Note, however, that there is a medical profession, called being a 'dietitian'. Dietitians are e.g. employed by hospitals to prescribe meals/diets for patients. Many hospital patients are delicate, e.g. diabetic, peri-operative, or with compromised internal organ function.

Dietitians are taught about diet. That is their job.

If fasting were healthy then presumably people would be fasting in hospitals. They're not.

If fasting were healthy then I would also expect fasting to be listed on a page like this one. It isn't.

The best you can say about fasting I think, health-wise, is that a limited amount of fasting might not be harmful: unless you're ill, old, young, pregnant, or working hard (in which case even a limited amount of fasting might be a bad idea).

It might improve you spiritually, who knows: fasting for Lent, or for Ramadan; or hunger strikes for political change. But there's no evidence that it's 'healthy'.