Fast Asleep: Intermittent Fasting, That Is

Intermittent fasting has been creating quite a buzz lately. It’s all the rage. Celebrity and entertainment magazines and websites tell us it’s what all the “cool kids” are doing. Just Google it and 62.5 million results show up.

And that’s just for the term “intermittent fasting”. There are so many other ways of referring to this concept, and so many different strategies. It can feel completely overwhelming. And if acronyms and numbers drive you up the wall, well then, say hello to your ceiling. For example: IF is obvious, right? That’s plain old intermittent fasting. But here’s just a small sample more:

EOD (every other day)
ADF (alternate day fasting)
OMAD (one meal a day)
TRF (time restricted feeding)
5:2 (5 days of normal eating and 2 of fasting
16:8 (16 hours fasting and an 8 hour eating window)
18:6 (18 hours fasting and a 6 hour eating window)
20:4 (well, you get the idea)

Despite all the lingo, jargon and gobble-de-gook, intermittent fasting is really a very simple concept. Sometimes you don’t eat. You skip a meal, or maybe two. You stop eating earlier in the evening than you normally do. The longer you let your digestive system rest between feedings (another IF term), as the theory goes, the better for you.

Full disclosure, I personally love IF. I’ve done alternate day fasting a couple of different times, and each time I’ve lost weight easily. Believe it or not, I actually enjoy the feeling of being empty. Not hungry, just empty. I feel less aches and pains and general creakiness when I’m IF-ing. I’ve learned that the feeling of physical hunger comes in waves, fading away pretty quickly, instead of continuing to increase, and that the waves become less uncomfortable and less frequent as I continue to fast.

But I’m not here to thoroughly explain what IF is or how to do it. That is more than adequately explained all over the internet.

I want to talk about how intermittent fasting can affect our sleep-wake cycle.

Sleeping and Fasting
It’s pretty obvious that, by default, when we sleep we are fasting. Unless you have the disturbing sleep disorder known as sleep-eating, this is the easiest fast you’ll ever do.

In earlier generations, people finished dinner and then didn’t eat again until they woke up in the morning. That easily provided a 12-hour fast. In our time, we seem to want to snack up until bedtime. If you eat as soon as you get up in the morning, you’ll get about an 8-hour fast.

If you’re trying to fast for longer periods, finishing your eating earlier in the evening and delaying (or even skipping) breakfast isn’t so tough because during most of the long hours of fasting, you’re unconscious.

Some people resist skipping meals because they think they’ll run out of energy and get tired or sleepy during the day. We’ve been told in the last 50 years or so that we should be “fueling our metabolism” and “keeping our energy up” by having regular meals and snacks all day long.

If you have blood sugar issues, this may very well be what you need to do. But most healthy people can easily go without food during part of their day without getting tired. Even all day. In fact, a recent study concluded that daily intermittent fasting does not result in more daytime sleepiness. This study was very small and limited in scope, and the researchers note that more comprehensive studies are needed in this area.

Another recent study on fasting and alertness, conducted in Saudi Arabia during the month of Ramadan, has shown that a wake-promoting neurotransmitter called orexin-A is produced by the body during fasting and concluded that fasting does, indeed, increase alertness. Again, the conclusions of this small study require further research to confirm the findings.

Survival of the Fittest….and Most Alert
While we wait for these additional studies to come in and fill in the blanks, the conclusions so far make a lot of sense. Early on in human existence, if we had gotten sleepy and felt low on energy whenever we didn’t eat, we wouldn’t even be here today. If those early humans had just laid down for a nap instead of going out to hunt or forage, we wouldn’t have gotten far, would we? They had to be mentally sharp, have ready energy and react quickly to get the food they needed. Same goes for the animal world. Wild animals feed when they’ve found food and when there’s no ready food source, they continue to search and hunt.

We may now be in the 21st century and living lives very different from the early days of humanity, but our bodies haven’t changed all that much when it comes to feast and famine. We are designed to go out there and find the fuel we need when we’re running low. For that, we must be alert.

Luckily, fasting appears to provide just that. Along with the preliminary clinical results we talked about before, there is quite a bit of anecdotal evidence as well.

This increased mental clarity and wow-level energy is a common topic on IF web forums and social media groups. I’ve seen people post about cleaning and organizing all their closets and drawers on a fasting day. Or waking up early and going out to exercise when they’ve never, ever wanted to do that before. It’s pretty amazing, the burst of energy that can come from not eating!

Another common theme on the boards, however, is that this energy and alertness can last into the night. Some people have distinct trouble sleeping when they’ve been fasting. It makes good sense, evolutionarily speaking, but it doesn’t make survival in our modern world any easier.

According to Dr. Jason Fung, MD of Intensive Dietary Management and a leading expert on intermittent fasting, trouble sleeping can be a common problem. He notes that increases in nor-adrenalin and cortisol can disturb sleep.

That, along with the increased orexin-A produced during the fasting day, can make it harder to sleep well.

Can you fast and sleep well too?
Many intermittent fasters sleep perfectly well with no issues. I’m one of them. I am very fortunate in the sleep department. I’m able to sleep well most of the time. And I haven’t noticed any pronounced changes in my sleep when I fast. I sure wouldn’t want anyone to be scared off of trying IF because they’re afraid they won’t be able to sleep well.

For some people, changes in eating patterns of any kind can cause some disruptions, and not just in sleep. Often it’s just a matter of simply being patient and allowing your body to adjust to your new regimen.

Dr. Michael J. Breus, Ph.D., Clinical Psychologist and expert in Sleep Medicine, provides some advice on intermittent fasting and sleep. Some of the things he recommends are to listen to your body and find out how you are reacting to fasting. He also says that tweaking your bedtime and waking up time can help if you find you’re struggling.

Hopefully, researchers will continue to study how fasting affects our sleep. And for those people who find it difficult to sleep while doing IF, I hope they can provide some really helpful information and advice to deal with those challenges.

We would love to hear your experiences with intermittent fasting and if or how affects your sleep. And don’t forget to share how your energy levels and alertness are affected during the day!