Tuesday, December 23, 2008

Intermittent Fasting Experiment – Update after 5 Months

During the fasting periods, there really is no spoon. (Photo by alicepopkorn)

It's now been over five months since I started my intermittent fasting experiment, which means it's time for an update.

To recap, when I started in August, I went straight for the 24/24 version of intermittent fasting. That means I eat for 24 hours and then fast for 24 hours. I usually either start or stop eating at 4 PM, so every other day I miss breakfast and lunch and every other day I miss dinner. On the other hand, I don't really think in terms of "three warm meals per day" anymore, so breakfast, lunch & dinner have sort of lost their meaning.

This kind of fasting is also known as alternate-day feeding (or ADF) in a lot of the mouse and rat studies. That's a fitting term for rodents, because they don't have the same sleep pattern that humans do; that is, they don't sleep 8 hours per night and then stay awake for 16 hours. Instead, they sleep short periods throughout the day and night and eat when they feel like it.

In humans true alternate-day feeding is difficult, because the fast would begin at 12 o'clock in the night and you'd have to go for an entire day without food. With intermittent fasting, where you can break or begin the fast in the middle of the day, you get to eat at least something each day. This makes it much more convenient for humans but still retains all the health benefits of ADF.

The obvious question in most people's minds is probably "What about the hunger?" Well, in the beginning hunger was certainly an issue. Even though caloric restriction had been much more difficult due to constantly being hungry and having to count everything, my first fasting periods were still somewhat hard to get through.

I then tried green tea and black tea, both of which were moderately effective at reducing the feeling of hunger. The best thing, however, was coffee, which not only reduced hunger but also improved my concentration and mood. I now start each morning with a cup of coffee, and it definitely has helped a great deal. I also drink green and black tea throughout the day, but it's mostly for other health benefits.

As much I love coffee and tea, the most important thing has been time. During the course of this experiment I've noticed less and less hunger during the fasting periods. I assume it takes a while for the body to get used to the new situation, where it suddenly isn't constantly provided with energy. Nowadays, I rarely feel extremely hungry even in the last few hours of the fast. Sure, I have a great appetite when it's time to eat again, but I feel very energetic during the fast. I've now even been able to hit the gym during a fast, which seemed quite difficult during the first two months.

At first I thought I felt less hungry because I was sleeping a lot (9-10 hours per night) and thus spending less energy. When I reduced my sleep to seven hours, I noticed I felt no more hungry, even though I spent more time awake (and got much more things done). In fact, I don't think I've ever felt so energetic during the dark winter months while sleeping this little.

So if you're considering giving intermittent fasting a go but have doubts about the hunger issue, rest assured that it will get easier with time. You could always start easy and fast for 12 hours, then 13, 14, etc. until you get to 24 hours.

One thing fasting unfortunately doesn't seem to have changed is the immune system; some people have said they haven't been sick since they started intermittent fasting or caloric restriction, but I'm currently fighting the flu virus unsuccesfully. Just in time for the holidays, too. Oh well, you can't have it all, can you?

Merry Christmas to everyone reading this blog!

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5 kommenttia:

Anonymous August 12, 2009 at 8:27 AM  

Very interesting! Thanx for your personal feedback on the intermittent fasting phenomena.

Chet March 4, 2010 at 6:57 PM  

Do you know of any studies done on IF with shorter fasting period? I'm only able to do 16 hr fast because of weight training and i can't deal with the hunger beyond that.

JLL March 5, 2010 at 11:16 AM  


Yes, there is at least one study that used a condensed eating window of 4 hours. I've discussed the paper in three parts.

I don't remember seeing other studies using shorter fasts, but I don't think 24 hours is any magic number necessarily. Any kind of fasting will have some benefits. If you do want to try longer fasts, keep in mind that the hunger will subside after a few hours. I also find that if I go to the gym towards the end of the fast, it's easier to prolong the fast.


Chet March 10, 2010 at 7:56 PM  

Thanks for the link. The fast gets easier each time. I'm trying to work my way up to 24 hr fasting window. This week i'm able to do 18 hrs. Next week i will try 24 hr fast.

Anonymous August 7, 2012 at 12:33 PM  

Have you lost body weight? Any change in body composition? That'll be interesting to know. Most of humans can withstand very well acute and long term fasting, just because of our hunter-gatherer ancestors that for thousends of years had been exposed to alternate periods of feasting and fasting! So no wonder that adopting intermitting fasting can work very well to keep a healthy body ...

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