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20 hours without food: The intermittent fasting experiment

Posted Jan 10 2010 11:23pm

Ed. note: This part 1 of a post that was written on Saturday after a day of trying intermittent fasting, or IF. Note that fasting is not starvation, and is a discipline that has been practiced for thousands of years by cultures around the globe. That said, I approached it as an experiment, with some pretty surprising results.

The idea of intermittent fasting (IF) has intrigued me for some time. I am a big fan of the website Fitness Spotlight , and have read their exhaustive research on the subject of IF several times, always wondering whether it is realistic for me. Today, I gave it a shot.

A little context: Before I tried the fast I had a doctor’s appointment at which I discovered a) that I had already lost two pounds on the year at that point, and b) my blood pressure was surprisingly good (122/78) despite increased stress right now. This was great news since it was a significant improvement from borderline high blood pressure a year ago, and made me feel as though my longterm dietary changes have helped my overall health. Of course one measurement is not enough to establish a trend, but I’ll take it until the next BP check. Although I am far from in ideal condition weight-wise, my other vitals appear to be pretty good.

Good news at the doctor’s office, even a little, is a great energizer.

Second, this morning I got up with the kids at around 7:00AM, and felt motivated to go hard after my general dietary goals. I realized that I hadn’t eaten anything last night after about 9:00PM or so. Having been reading about the paleo/primal methods of eating over the past few days, and the use of intermittent fasting in combination with it, it occurred to me that I was in an ideal state to give it a try. I knew that I had a 3-mile run scheduled for the afternoon, so I was curious to see not only how I would deal with it throughout the day, but how it would affect my energy levels.

Why fasting?

In the bigger picture, I am intrigued by fasting because in a sense it de-emphasizes food as something to obsess about. Current trends in the diet world often include eating lots of small meals and pre-packaged snacks to “keep the fire burning”. I think there is some merit to this perhaps (stabilizing metabolism makes sense intuitively); but I think the opposite end of the spectrum is worth exploring. In many countries around the world people do not seem to need to eat constantly just to stoke the fires; when it’s time to eat, it’s time to really eat. When it’s time to do something else, food isn’t part of that activity. I’m not sure which way is better, but I have a feeling that thinking about food all day long by scheduling everything around 6 or more eating times and bringing snacks and drinks with us everywhere from car rides to doctor’s visits may not be the best solution.

That was a long way of saying I enjoy keeping an open mind on the subject, especially because there are simply no one-size-fits-all absolute truths in diet and exercise.

I also think that giving your digestive system a break, or an opportunity to recover, makes intuitive sense. Whether or not it leads to effective cleansing and restoration I can’t say; but it seems logical to give such a vital system a break once in a while.

[ed. note: I'll discuss more of the benefits in part 2.]

Quick summary of intermittent fasting (at least the way I did it)

For the uninitiated, the rules of intermittent fasting are relatively simple: No food at all for a set period of time, but water is fine. Water with lemon is preferred in part because it helps with hunger and additionally because it’s good for your liver. Note that in religious disciplines it is not uncommon for water to also be prohibited during a fast. This is far from a religious thing for me, so I opted for the water.

One of the chief strategies in intermittent fasting is to use your sleep time to your advantage. Sleeping for 6-8 hours means you don’t eat during that period; so starting a fast the night before is a great idea, and ultimately what I did.

Generally folks who fast successfully seem to fall into two categories. Quoting from Mike’s article on Fitness Spotlight (“ Intermittent Fasting 101: How to start burning fat “):

  • Daily Fasting: Typically done every day and only giving the person a smaller eating window in which to get their calories. (for example, a 18hr daily fast would mean someone would only eat every day between the hours of Noon and 6pm). You will see varying times from 15-19 hours for daily fasting as seen with the Warrior Diet , Leangains , and Fast-5 approach.
  • Fasting 1-3x a week: This could also be called alternate day fasting/calorie restriction (for those doing it every other day). This is just fasting of usually longer periods 18-24 hours but only 1-3x a week. Many variations to play with here like the Eat Stop Eat method (24 hr fasts 1-2x a week).

I chose the latter option, fasting for 20 hours.

Finally, another key to fasting is what is called “clean eating” during eating times. This basically means eating whole foods with an eye on nutrients and meeting caloric guidelines. Again, the idea is that if you need to be eating at a calorie level that will keep your metabolism flowing, but if you are trying to lose weight, that you maintain a healthy caloric deficit. I’m not too concerned about the calories; but the nutrition is essential.

Heavy disclaimer: I should take a moment to note that if this is something that interests you, you should definitely read not only the Fitness Spotlight article, but do your research, talk to a doctor, etc. Fasting is certainly not for everyone, particularly people with known or underlying health conditions. This particular article makes it pretty clear that there is no magic formula for fasting that will work for every person. Your approach to fasting may be radically different from another person, ranging from a wider window of eating daily to 24 hour periods. Combining exercise can be effective, but it depends on whether you are an irregular exerciser or an athlete in perpetual training. In other words, this is not a one size fits all situation – there are simply too many variables. As Mike says, if something isn’t working for you, change it!

Common fears of fasting

If you read any of the forums where folks discuss the idea of fasting, you quickly notice that people generally fall into either the “I do it and love it” camp or the “oh my Lord that is so bad for you/dangerous/I could never do that/you could die” group. I am somewhere in the middle – listening to the concerns on one hand, but interested in the benefits as well.

The most important factor that seems to get confused is that contrary to the fearful mindset, you are not starving yourself. You are simply changing the time at which you eat. In fact, the idea is to reduce the window during the day in which you eat, but when you do eat you emphasize greater quantities of whole foods that provide the necessary nutrients and calories for a healthy diet.

The mental game

As longtime readers of Almost Fit know, I have clearly identified that food has some significant emotional ties for me. In fact, that is the biggest challenge for me diet-wise. The physical feelings don’t generally bother me when I’m less than full; it’s the emotional part that gets a little (or a lot) funky. When I’m trying to make a significant dietary change I almost always get irritable and, on a bad day, a sense of “hungry desperation” takes hold. I can get quite emotional about it, and completely irrational. Not fun.

So how would IF affect my emotional state?

Additionally, I purposely avoided activities that might bring out cravings. Television was off limits, as well as any reading on new recipes for lemon bars or smoked bacon.

The physical game

Physically I wasn’t sure what to expect, but I had a strategy: Stay busy, and stay hydrated. Simple as that. I knew for sure that I’d feel the pangs of hunger, but I was more curious about the blood sugar effects.

I was also really interested in my overall energy level with no food; so often we convince ourselves that lack of food is the cause of low energy, when in reality it may be that the real culprit is poor food choices.

Lastly, knowing that I had a 3 mile run scheduled, I was really interested to see how I’d feel pushing exercise on nothing but water. Would it cause low energy, cramping, lightheadedness, or worse?

Going for it

With a plan in hand, I chose to go for it – I decided to try a 20 hour fast, which meant I would not be eating until 5PM. I also knew that if things got too frenetic I wasn’t exactly stuck on a desert island; I could always stop if it started to feel wrong.

So how did it go? Stay tuned for part 2.

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