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?

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    So the question is, "Is it healthy to have no food whatsoever (except water) for 2 weeks or 30 days"?
    – ChrisW
    Commented Jun 3, 2011 at 23:28
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    I'd reccomend checking out the book 'the great starvation experiement' or if you really have the time (it's 2 volumes and about 1500 pages) Ancel Keys' original work that book is based on, called "the biology of human starvation" (hard copy for this one's pretty expensive; check online or library). Commented Jun 3, 2011 at 23:56
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    I've never had a doctor recommend fasting, as opposed to "don't eat in this period" before surgery or a blood test. Somebody can recommend fasting to treat illness, and I can recommend treating anything that person says as likely wrong. Commented Jun 4, 2011 at 2:37
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    One more definition is needed. What constitutes a "toxin" that this will supposedly flush out?
    – JohnFx
    Commented Jun 4, 2011 at 19:39
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    Fasting means different things in different cultures. For example a Muslim may fast during eid where they will not eat during the day, but after a certain time they can eat normally. A Hindu on the other hand may remove nuts from thier diet for a week. A christian may give up something they like for lent (e.g. chocolate). These all differ from the definition you have supplied so the question is what does your friend mean by fasting? If you went without food and only drank water for 30 days I can't seeing that being particulary healthy or beneficial.
    – Ardesco
    Commented Jun 6, 2011 at 15:02

1 Answer 1


As for "increasing immune system", there may actually be some truth in that:

Here, we show that prolonged fasting reduces circulating IGF-1 levels and PKA activity in various cell populations, leading to signal transduction changes in long-term hematopoietic stem cells (LT-HSCs) and niche cells that promote stress resistance, self-renewal, and lineage-balanced regeneration. Multiple cycles of fasting abated the immunosuppression and mortality caused by chemotherapy and reversed age-dependent myeloid-bias in mice, in agreement with preliminary data on the protection of lymphocytes from chemotoxicity in fasting patients.

Source: http://www.cell.com/cell-stem-cell/abstract/S1934-5909(14)00151-9 (I do not have access to the full article, and the summary does not give the actual results nor methodology).

Article: http://www.eurekalert.org/pub_releases/2014-06/uosc-fts060214.php

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