Is Fasting Beneficial?

Mr. D. S. of Saratoga, CA asks: Hunter-Gatherers eat natural food and exercise and get almost no degenerative disease. But they also fast, so shouldn’t we fast?

Great question. I used to think so, but had to change my opinion. In the past I encouraged fasting. My starting point was 24-hour fasts. In some cases I experimented with longer fasts pand different intervals between fasting in order to improve various blood markers and, interestingly, it often worked, but only at first. After regularly fasting for some period of time most of my patients’ bodies found some way to compensate, usually subconsciously. The numbers returned to their earlier values, and for some, actually got worse and were accompanied by fat weight gain. So starting about 3 years ago, I began advising people not to fast. There are exceptions but we humans do not take lightly to fasting.  I know, I have watched many people over the course of years and with rare, very rare, exception fasting always backfired. The compensatory mechanisms are very subtle and very powerful.


This is a very good example of Quantitative Medicine. Logically, fasting should have worked. But it didn’t. The numbers define and quantify health and must be acknowledged, even if that means I have to change my recommendations.

There are two sides to fasting, one good, one not. The good side is that it gives the body extended time to clean out damage and to repair. I have seen profound examples of this in the past. However, the bad side is that fasting is a catabolic state. The body may well decide to conserve rather than repair; to tear down rather than to build up.

A second important point is the hunter-gatherer lifestyle itself. It is true that degenerative disease is rare in hunter-gatherer populations, but we need to identify the reasons for this. Certainly eating parasite-ridden food would not be a good idea. This could, and frequently would, kill you. The principle hunter-gatherer attributes that I believe worthy of emulation are: 1) a natural food diet, 2) frequent explosive exercise, 3) connectedness to their world and their community, and 4) getting a good nights sleep.

However, several other hunter-gatherer attributes are to be avoided: 1) parasite-ridden food 2) unavailability of treatment for infectious disease, 3) unavailability of treatment for wounds, 4) inter tribe warfare, 5) childbirth issues, and, recently added 6) fasting.

So again, it is good to take what cues we may from the hunter-gatherers, but each one needs to be examined for its own quantifiable merits.

The body has incredibly powerful metabolic regulation. It can shut down energy consumption if there is a food shortage, or, amazingly, if it detects anything that might signal that a food shortage is imminent. Skipping a meal is an obvious example, as would be a diet that featured calorie restriction, such as Weight Watchers.

Other activities can signal food shortages as well. For instance, if you are doing a lot of walking, a round of golf perhaps, the body may interpret this as migration, and why would you migrate? To seek a new hunting ground, so there must be a food shortage coming. The system shuts down.

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