FASTING CAN BE GREAT –– AND IT CAN BE DANGEROUS

by Nils Osmar. This article should not be construed as offering either formal or informal medical advice. The content is intended solely for informational purposes. Any changes in your lifestyle or diet should be done in consultation with your doctor or health care professional.  


  • I’m an advocate of fasting. Doing it carefully and methodically, starting with long fasts and gradually building up to longer fasts, has done wonders for my health. 
  • But it’s important to recognize that fasting can be dangerous. It can contribute to micronutrient deficiencies, and to the formation of kidney stones, as one Youtuber found out (see the video at the bottom of this page). (The man in the video blames himself for eating the “wrong” foods at the end of the fast, but it’s clear that he was doing a three week water fast without medical supervision, which is extremely dangerous in itself, even if all had gone “right.”)
  • THIS ARTICLE by Dr. Jason Fung points out the many benefits of fasting, but also points out its dangers and why it must be done safely. His advice is essentially that if you don’t know what you’re doing, don’t do it. You can NOT just jump into fasting without a plan, without understanding how it works, anymore than you could jump into driving a car on the freeway if you’ve never had a driving lesson.
  • Here’s a short excerpt from Dr. Fungs’ article:

“People get into trouble with extended fasts because they don’t follow common sense. Many of these fasting retreats offer 30 day water only fasts. If you become depleted of sodium (quite common), there are no doctors there to monitor for warning signs.

“If you become very weak and unable to get out of bed, there is very clearly something wrong, and you should not continue fasting. This is common sense. In my IDM program, clients know that they may feel hungry, maybe a little irritable, constipated perhaps, but they should not feel UNWELL.

“If you are really feeling poorly, you must stop. There is no reason to continue, because fasting is free. It is far better to stop and try it again (if you want) in a few days when you are feeling better. The problem with these fasting retreats is that people have paid money to be there and therefore they push on far beyond the limits of good safety practice and far beyond the limits of common sense.

“Further, people undertake extreme fasting without any kind of preparation. Instead of undertaking shorter fasts and gradually extending it, they immediately opt for a full on water-only extended fast. This is like a rookie mountaineer that decides that he/she will tackle Mount Everest, without oxygen and push on to the summit irregardless of weather. The experience mountaineer would immediately recognize this as a death wish, but the rookie has no inkling of the dangers and may come home in a body bag. It’s pure stupidity. Yet fasting clinics promote this very same idea.

“Taking the most extreme fast (water-only fasting, as opposed to allowing some bone broth or some caloric intake), to an extended period of time (30 days instead of 1-2 days), in anybody irregardless of whether this is medically appropriate, without any adequate medical supervision or access to bloodwork? I can tell you right now, that’s pure stupidity.

– Dr. Jason Fung