A few months ago, a neighbor informed me that she and her husband had learned that fasting (that is, eating no solid food and drinking only clear, noncaloric fluids for a specified length of time, from several hours to days or weeks) has been shown, by empirical research, to have a number of health benefits. She directed me to some books and videos on the topic that captured her spouse’s attention. He has cancer and was intrigued by recent scientific publications that show fasting before receiving chemotherapy puts healthy cells into a protective mode and throws tumor cells into disarray. The result of these cellular state changes appears to be the enhanced targeting and killing of cancer cells by the chemotherapy. Fasting has numerous other advantages as described by health professionals, including help preventing and combating type 2 diabetes, improved energy levels, sustainable weight loss, and a general feeling of well being. I was fascinated by this information on an activity I have only ever associated with religious observance and as preparation for medical procedures such as blood tests and surgery.

As I do with any new interest, I read extensively on the topic. There are many books, articles and even a few documentaries on the science of fasting. (I include a partial bibliography below.) I reviewed many descriptions of the effects people have experienced while fasting and found that it is quite safe to fast for more than 24 hours. Extended fasting even makes sense from an evolutionary standpoint. Ten thousand years ago humans could not rely on three square meals every 24 hours and it is entirely likely that our ancestors went days and, at particularly lean times, weeks without substantial meals. Many proponents of fasting as a healthy way of life maintain that we have not evolved to eat the vast quantities of food that we do today and propose that overeating is fundamentally unhealthy and the cause of many a physical ailment.

Once I was convinced that it would be perfectly safe to not eat for more than 24 hours, I decided to try a fast of moderate length. Five days seemed doable. Besides, Mahatma Gandhi, Cesar Chavez, Upton Sinclair, and others famously fasted for weeks at a time. And it turns out that, at least since the early part of the 20th century, there were physician supervised programs in the US and Europe that provided retreat style environments where people fasted for as many as four weeks. Today, fasting clinics are again gaining in popularity in the US and Europe. As an added plus I could tell my neighbor with cancer what to expect before he went on his extended fast prior to his chemo. 

The longest I had previously gone without food was 24 hours, never longer. The literature suggested that between 24 and 36 hours into the fast my body would switch from using glucose to fat. This was to be an entirely new experience, because I had never been without food long enough to go into ketosis (the metabolizing of adipose tissue to produce ketones as a primary, life sustaining fuel source). The use of ketones for energy reportedly leads to sharper thinking and might be responsible for the religious fervor and “closeness to God” that some extended spiritual fasters report. Also, after 48 to 72 hours much of the hunger and discomfort of going without food is supposed to dissipate. The guides made brief mention of the need to drink water throughout the fast, but this seemed like a no brainer to me. It turns out that there could have been a little more detail on fluid consumption.

Day 1 was quite easy. I should add that I don’t tend to eat much under normal circumstances and often can go all morning and most of an afternoon without feeling hungry. 16 hours in I began to feel peckish, but the cravings were mild and I ignored the occasional twinge and was able to distract myself with my usual daily activities.

The next 24 hours of Day 2 were the roughest and most eventful of the entire 120 hour fast. The second night was much more challenging than the first (which makes sense, since I went to sleep the first evening about 4 hours after having my last meal. I wonder if hunger exacerbates existing weaknesses. The difference between how I felt during the day and at night (after 24 hours without food) was, well, day and night. I had a lot of trouble sleeping. I usually have issues with insomnia and I was restless in a way that I did not associate with hunger, though I did some cravings - but not to the point where everything looked like a turkey dinner (as in cartoons). I fell asleep ok, but at 2:00am I was awake and strangely agitated. The rest of the morning I dozed off only to wake up half an hour later, again and again, which is worse than my usual sleep disruption. And every time I woke up it was to an anxious feeling, restless legs, and a nagging buzz in my head. I wonder if the nights were particularly bad because these were occasions when I could not rely on an abundance of activities to keep me distracted from the monkey of hunger my back.

By mid-morning I had a terrible time concentrating, was cognitively spaced out, and had a mild tummy ache. I was confident I could break through the concentration issues, except that my efforts to focus were interrupted every 20 minutes by the urgent need to pee. I was drinking a good amount of water. (This was something that all the literature mentioned, the importance of abundant fluids.) I started to think that I must be getting more than enough liquid because my urine was clear (sorry, these details are important) and everything I drank seemed to run right through me, so I stopped paying special attention to my fluid intake, figuring I had more than enough hydration. Despite trying to heed all the warnings, By 4:00pm I had a raging headache. I started to worry that I was still drinking too much water, resulting in an electrolyte imbalance. Yet I was thirsty, an indication of dehydration. I was feeling quite ill at this point, not weak from hunger, but kind of like I had heat stroke. “But I’m super hydrated,” I thought. 

Then it hit me! I was getting no salt. 

Sodium helps your body to retain fluids. Without salt my system was releasing more and more fluid. The water I was drinking was literally running right through me; none of it was ‘sticking.’  I did some quick research and confirmed that the lack of sodium was very likely contributing to dehydration. There were only two ways to deal with this, drink constantly or replace the salt I was no longer getting with food. I considered adding salt to my water (sodium has no caloric value) to allow my body to “hold on to” fluids and avoid peeing every twenty minutes, but that did not sound very palatable. Then I remembered that I had electrolyte replenishment tablets left over from hiking during the hot Summer weeks. I decided to add these to my water after I determined that they added a negligible number of calories - 8 per 16oz. The rest of the day, I drank electrolyte enhanced water and, though I still did pee more than usual, it became more manageable and my headache and thirst receded over the course of several hours. 

The evening of the Day 3 was still filled with a restless and fitful sleep. The next morning it was easier to get up early and get to work because I was not tired despite another bad night. I had an abundance of energy and I can’t say I was either more clear or foggy headed. I felt different. Ready to go, go, go. The hunger had completely disappeared and I got through most of the day without distracting thoughts of food (that is until I had to cook for the rest of my family - though this was not as difficult as you might expect). I even went for a brisk 4 mile hike. 

Over the next couple days it became more and more apparent to me that physical activity kept my spirits up and always led to a feeling of well being, more so than usual. I had plenty of energy and moving about turned out to be the perfect antidote to the occasions when I was at all tired or spacey. The rest of the day unfolded like any other. I did my writing and reading and various chores. I did have to shop for food and make dinner for my family. Visiting a grocery store and cooking, though not nearly the torture I thought it would be, was different. As one makes some excessive food purchases when hungry, I bought a little too much food; everything looked delicious. When I cooked, I prepared more than my wife and kids could eat (though this might have been because I am not used to preparing meals for three.) 

The evening of Day 4 I still had trouble with sleep. I did not have any particular discomfort. I was awake more often. As soon as I embraced it and resolved to listen calmly to an audiobook without any expectation of sound sleep, I was far more comfortable and no longer tortured by the situation. I figured that if I was tired in the morning, I would deal with it somehow. Later, that afternoon, I did take a 20 minute power nap and even had some green tea, which, now that I was properly hydrated and retaining fluids, I decided I could drink without concerns of water loss due to the stimulating affects of caffeine. The day toddled along much as the previous one. I had energy and was physically active without feeling exhausted or unable to concentrate. I was a bit disappointed not to experience any super focus or deep feeling of spiritual connection to the world or the divine. 

One surprise during the last 72 hours of my fast was that my meditation was easier, which was the opposite of what I expected. I practice a hybrid of zazen and mindfulness. As the fast progressed I found I could more effortlessly clear my head and allow sensations and perceptions to flow through me without my mind reaching out and grabbing at reality to turn it over and skip along to some random, yet associated, thought. I guess I can say that my meditative experience was more spiritual in that I was more quickly able to reach a clearer, cleaner connection to the heart of the Universe with less effort. Still, I don’t think this comes close to the religious fasting experiences I’ve read about and heard described. There was no awe, no deep abiding sense of oneness with the Divine, no transcendence. Perhaps I need to fast longer and meditate more during my fast. Though, to be clear, transformative spiritual experience was never a goal of my fast.

At the start of Day 5 (the final 24 hours of my fast) I settled in for an evening of listening to my audiobooks and was thus surprised when I slept through the night, only waking a couple times for a few minutes. I did still wake after only six hours of sleep, but was refreshed and ready for action. I was most tired on this final afternoon and eventually needed a power nap to get back to a productive mindset. 

By the end of Day 5 I was more than a little worried about how I should break my fast. I had read that one should not stuff their gullet with a heavy meal at the end of an extended period without food. So, of course, I had the best of intentions. I thought that I would have a light broth, perhaps some fruit or veggies, a slice of toast. I started out with a vegetable soup and some green beans, but this rapidly devolved into a bunch of green beans, a full can of chili, a large bowl of ice cream, three generous slices of pound cake, and a cup of yogurt and granola with honey and berries. I ate all this in about three hours. The truth of the matter is that once I started eating my hunger reemerged with a vengeance. Thankfully I suffered no tummy ache or insulin rush. And I slept really well that night.

I wonder whether, if I had continued to fast after day five, I might have continued to sleep through the night with ease. Perhaps day three and four were a transition period for my brain to operate on ketones, rather than glucose. I have resolved to do a seven day fast in the next few months to see what the effects of two more days might be.

Also, I shed lot fewer pounds than I expected. I don’t know why, but in the back of my mind, I had this unreasonable worry that I would have to stop early due to excessive weight loss. At the end of the fast I had only lost about 6 pounds and I am pretty sure at least a third of this was water (because I gained a little less than three pounds in the 24 hours after my fast ended.) 

All in all my experience with an extended fast was a good one. I learned that we can survive and, indeed, thrive without three square meals a day. I think this makes sense, given our evolution. As I mentioned at the beginning of this article, it is only in that past half millennium that large numbers of people have been able to rely on one or more repasts a day. Hunting and gathering ten thousand years ago, our ancestors must have gone through periods of feast followed by days and, even, weeks of fast.

At the end of my fast I felt lighter, less bloated, and more energetic. I will try to do this every few months. I also consider it great for the development and maintenance of self discipline and willpower. And there is something to be said for challenging and debunking some modern society myths (that we need to eat multiple substantial meals a day, and that a person will become lethargic, useless, and near death after not eating for a couple days) that have certainly contributed to rising obesity rates, increasing type 2 diabetes diagnoses, global warming, the widespread water shortages, and the disproportional distribution and usage of world resources.

Bibliography

Sinclair, Upton. The Fasting Cure. Kalpaz, 2017.

Fung, Jason, and Jimmy Moore. The Complete Guide to Fasting: Heal Your Body through Intermittent, Alternate-Day, and Extended Fasting. Victory Belt Publishing, 2016.

Vanderschelden, Michael. The Scientific Approach to Intermittent Fasting: Find out How a Simple Lifestyle Change Can Completely Transform Your Health and Your Life! Dr. Michael Vanderschelden, 2016.

Wilson, Jacob M., and Ryan Lowery. The Ketogenic Bible: the Authoritative Guide to Ketosis. Victory Belt Publishing, 2017.

Gilman, director. The Science of Fasting. Grand Angle Distribution, 2016.

Orchard, Doug, director. Fasting. 2017.