The Every Other Day Fast

For the past four years, I’ve been experimenting with various types of fasting. When it comes to diet, I’ve found that there’s contradicting research for just about everything, so I like to incorporate different ideas and pay attention to how I feel as a result. I tend to think the body is pretty good at telling you what it does and doesn’t like – you just need to pay enough attention to notice. So this February, I decided to try out a more rigorous fasting regimen than I’ve ever done: only eat half of the days. For the most part, this worked out to eating every other day, but there were also a pair of 2-day fasts, each followed by 2 eating days. I’m glad I did it, and enough people have asked about it that I figured a post was in order. Here are the things I learned and observed over my month of only 14 eating days.

Before beginning, I should say I’m not a professional and this is all anecdotal, so I can’t suggest anyone do a similar experiment – come to your own conclusions. I also won’t go into the research on the matter, but if you want to learn more, looking into intermittent fasting, water fasting, autophagy, and ketosis should provide you with a lot of info.

For starters, the answer to perhaps the most obvious question is: yes, I lost weight. This wasn’t the intention of the experiment, but it was nearly impossible for me to eat twice as many calories as usual on the eating days, so I did lose a noticeable amount of weight. This isn’t all that interesting, but what is interesting is that I also got stronger over the course of the month.

Many people who lift a lot tend to over-exaggerate the need for protein and steady calorie input, and thus advise against fasting if you want to get stronger. As someone who only eats meat 1-2 times a week, I already believed this was mostly propaganda from the fitness supplement industry, but I was expecting to have trouble adding muscle. Ultimately, it ended up being my best month for muscle-building in at least 3 years. To achieve this, I maintained the same workout schedule as any other month, except that I had more energy overall, and thus tended to workout harder and longer than usual. Besides the first 3, the workouts on fasting days weren’t any harder than a typical workout. The most interesting thing to me was that I set a significant PR near the end of both of the 2-day fasts, after over 44 hours of without a single calorie. The human body is capable of much more than those being babied by modern developed society tend to realize, and that was on full display to me this month.

The highlight of the experiment to me was after my workout on Feb 15, the second day of my first 2-day fast. That night I had this strong feeling that I had broken free from one of the chains that constrains humans, particularly in wealthy countries, to a society-defined version of ourselves. I was experiencing something that humans were made to experience but that many no longer do because, for better or for worse, it isn’t necessary anymore for those lucky enough to afford a steady stream of food. I felt a connection to past generations of humans, who weren’t much different, if at all, than today’s humans other than the society they existed in. It provided a new perspective on life that I’m glad to have experienced, and I in fact at one point felt bad that so many people would live their lives without experiencing it. If for no other reason, this night alone made the whole month worth it. To a lesser but still significant degree, this experiment as a whole made the month feel like it meant something more than the average month. Once in a working routine, months can go by when nothing particularly novel happens. I hate this feeling, and this experiment certainly prevented it.

Towards the end of the month, my roommate pointed out how I seemed to save a lot of time by fasting, while he could spend over an hour preparing food on a regular basis. I had noticed this myself, and it was one of the nicer unexpected perks of the routine. I felt I could get much more done on fasting days. This gave me a new appreciation for just how much people allow their hunger to dictate how they spend their time, and I noticed this appreciation changing my time management habits on days when I did eat.

Thus far I’ve only mentioned the positives, but there were some negatives. The biggest one was that it was harder to plan my meals. Most weeks I make a large portion of food on Monday and eat it Monday-Thursday. While fasting every other day, food needs to last twice as long if I’m to make the same size batch. This never fully worked itself out, and is the main reason why I won’t be continuing this regimen. At the moment, I’m planning on having one fasting day a week but no more. I also had trouble focusing for a few hours every fasting day, though that got much better as the month went on, and as I got better about keeping my electrolytes stocked via salt in my water. Beyond that, the drawbacks were trivial and more interesting to observe than anything else. First, I felt noticeably colder after about 20 hours of fasting. I had to plan my outfits accordingly in fasting days. Next, fasting makes your breath smell bad, and I’m not sure why, so gum and mouthwash came in handy. There were also some similar observations that weren’t negative, like that I got tired earlier on fasting days, and that my sense of smell would get significantly better.

One effect I’ll certainly test again next time I can (hopefully not soon) is the impact on recovery from a cold. In the first half of the month, basically everyone I work with came down with a fairly nasty cold that lasted over two weeks in some cases. I noticed a cold coming on during an eating day, and was interested but also nervous to see what would happen with fasting involved. The next day the symptoms were worse but still only about 50% of typical peak cold conditions. In a normal scenario I’d have expected the worst of the cold to still be two days away. Fasting was a bit harder that day since sickness will dwindle your willpower. I pushed through, and around 9:00 PM was about to go to bed because fasting + cold meant I was tired very early. Then, within the span of a single minute, all of my symptoms went away. None of that is an exaggeration. I sat in amazement for about 5 minutes wondering how such an abrupt change could happen. I stayed up until 11:30, which is my normal bedtime, and felt perfectly fine. The next day there were some symptoms, but it was a typical last day of a cold, when you’re about 90% better, but a few symptoms linger. The day after, I was completely healed. I’ve never had a recovery this drastic, and I would be surprised if fasting wasn’t a key factor.

At this point I’ve told you most of the interesting outcomes of the every other day experiment, but I haven’t mentioned perhaps the most important factor of all: how I felt day-to-day as a result. First of all, it was pretty hard to fast the first few times, I will admit, but by the end of the month, it was extremely easy. I almost ate on a fasting day towards the end of the month simply because I forgot I was fasting. It was 8:30 PM and the thought didn’t even cross my mind that I hadn’t eaten anything all day - that’s how easy it became. By the end, my energy levels on fasting days were roughly equivalent to my energy levels on normal days prior to this month. Earlier on, my energy levels were lower on fasting days. On non-fasting days, I had tons of energy and was almost always in a really good mood. There were some eating days I had trouble falling asleep because I had so much energy I couldn’t make myself tired - something I hadn’t felt since high school. This was remedied by longer workouts when I had the time.

The plot below shows my self-reported energy level each day on a 0-10 scale. You can see that the first half of the month had a large gap between fasting and eating days, but by the end the gap was closed. There were other factors at play causing the late-month drop-off, like amount sleep, what foods I ate, and a busy end of the month with traveling and moving apartments, but the difference between consecutive eating and fasting days suggests that my body got used to fasting by about halfway through.