Last Updated on April 12, 2024 by Fasting Planet
SleepFoundation.org recommends the average adult who’s 26 to 64 years old sleeps for seven to nine hours a night. You always try your best to get your Zzzs, but soon, you’ll make a major lifestyle change through fasting. Will fasting make it easier or harder to sleep?
Fasting can admittedly cause sleep difficulties for the first few days you do it. Within three to seven days, you’ll start sleeping better, experiencing fewer leg movements and sleeping soundly throughout the night. This is due to how fasting can bolster your circadian rhythm.
Before you begin fasting, we recommend you read this article. You’ll learn what you can expect of your sleep on a fast, how your sleep can change for the better, and we’ll even throw in some tips for getting more Zzzs when you’re hungry. You won’t want to miss it!
Does Fasting Make It Harder or Easier to Fall Asleep?
According to a 2016 article in Consumer Reports, in the United States, up to 27 percent of a survey of 4,023 adults reported having sleep troubles. They either couldn’t fall asleep or stay asleep. You may already have sleep issues yourself, and you’re curious what will happen when you start your fast.
So, does fasting make it easier or harder to fall asleep?
The answer is both.
The first few intermittent fasts you go on are not necessarily easy. If you’ve never subjected your body to such long periods of not eating, then you can expect a slew of side effects. You’ll feel tired, cranky, hungry, mentally foggy, and perhaps even physically weak.
All day, you think about that glorious moment of your head hitting the pillow when you can blackout for the night Yet when bedtime arrives and you finally crawl into bed, you can’t sleep. Instead, you become hyper-focused on how hungry you are.
Even when you eventually do drift off, your rumbling tummy inevitably wakes you up. This happens all night, off and on. You drag yourself out of bed the next day, even more exhausted than before. Perhaps the problem persists even into a second night.
You have to think about what’s happening to your body during a fast from an internal perspective. You usually eat at least two meals a day, perhaps even three. Now, you’ve gone from that to maybe one meal or none depending on which intermittent fast you’re on.
Your body is wondering why you’re not eating. From your brain to your digestive track, all parts of your system are trying to make sense of this change. That, combined with the intense hunger, can leave you sleepless on the first few nights of your fast.
Sleep, Fasting, and the Circadian Rhythm
Getting quality shuteye at the beginning of your fast isn’t easy, and we won’t pretend and say it is. As hard as it can be, it’s worthwhile to keep following your fast, because this period of sleep difficulties won’t last forever.
Within three days of fasting, and for some as long as a week, you actually begin sleeping better on a fast. Is it simply that your body has adjusted to the lack of food and your new schedule?
That’s part of it, but it’s not the whole story by far. Your circadian rhythm plays a big role in your sleep quality, and fasting can impact circadian rhythm for the better.
What Is the Circadian Rhythm?
We all have an internal clock within us known as the circadian rhythm. This clock runs on a cycle of 24 hours and dictates which hours we spend asleep and which ones we’re awake. Your circadian rhythm determines this by the hours that are daylight and those that are dark. If it’s dark out, you should be asleep, but in lighted conditions, your circadian rhythm pushes towards you being awake.
The way your circadian rhythm makes you sleepy in dark conditions is by triggering melatonin, a sleep-wake hormone that comes from the pineal gland.
That midafternoon slump you may experience when not fasting isn’t entirely based on what you had for lunch. It’s also due to your circadian rhythm and energy regulation. The middle of the afternoon is when your energy begins its second decline of the day. The first decline happens when you’re not awake (or at least, when you shouldn’t be awake), sometime around 2 a.m. and 4 a.m.
Your circadian rhythm doesn’t stay the same throughout your life. When you were a child, you started to feel tired probably around 7 p.m. or 8 p.m. As an adult, you might go to sleep at 10 p.m., 11 p.m., or even later depending on your daily schedule. In your senior years, you may again start going to sleep even earlier, and staying asleep can be difficult.
Lots of factors can interrupt your circadian rhythm, likely interrupting your sleep as well. If you have a job that requires you to work throughout the night and sleep during the day, that will really screw up your internal clock. The same is true of a schedule where your sleep-wake times are drastically different from day to day.
Flying somewhere and experiencing jet lag can interrupt the circadian rhythm, as can spending too long looking at your phone or another device in bed. The blue light these devices emit can confuse your body into thinking it’s time to be awake.
Food and the Circadian Rhythm
Another factor that can impact when you sleep and how well is what time you eat. Three hours after consuming your last sizable meal of the day, typically dinner, you should go to sleep. This allows your body to prioritize digestion when you sleep so the quality of your rest improves. Also, cutting off your eating at around 8 p.m. is good for controlling weight.
In a 2017 report in Current Biology, the researchers noted that “circadian rhythms, metabolism, and nutrition are intimately linked.” In their study, 10 male participants altered their diets for a period of 13 days. They would eat meals every five hours, including breakfast, lunch, and dinner. Half the men began eating 0.5 hours after waking up, or 30 minutes, and the other group waited 5.5 or five and a half hours after waking up to begin eating.
Those that ate early did so for six days, then switched to later meals for the rest of the experiment. Then the participants’ respective circadian rhythms were tracked. While the participants did not feel more tired than usual when they ate early, during late meals, it was a different story. The participants had lower glucose concentration and reduced plasma glucose rhythms.
The study concluded that “human molecular clocks may be regulated by feeding time and could underpin plasma glucose changes. Timed meals therefore play a role in synchronizing peripheral circadian rhythms in humans and may have particular relevance for patients with circadian rhythm disorders, shift workers, and transmeridian travelers.”
Fasting and the Circadian Rhythm
That brings us back to fasting. You now know that eating later in the day can affect your blood glucose. Alaska Sleep Clinic says that when you sleep less, your blood sugar goes up and thus keeps you awake even longer. You could even be at an elevated risk of developing diabetes if you’re sleepless often enough.
When you’re on a fast, you’re limiting your eating, doing so in small windows if you can eat at all. You might assume then that fasting could make it easier to sleep since your blood sugar will be lower, but is that the case?
It is indeed. Not only is it the lack of late meals through fasting that makes it easier to sleep, but the impact that fasting has on your circadian rhythm. In a 2017 report published in Cell Metabolism, the data concludes that it’s possible that fasting could strengthen your circadian rhythm. Your levels of melatonin, which makes you sleepy, go up, and your insulin levels may also drop.
A solid sleep-wake cycle makes it easier to regulate your energy, which is important when fasting, as you have less energy to go around. You’ll also be able to get to sleep faster and enjoy better-quality sleep through fasting.
Can You Sleep Longer When Fasting?
By now, you’ve learned that while it’s hard to sleep on the first few days of your fast, that that won’t be the case for longer than a week. You may find it easier to fall asleep at that point, but what you’re worried about is waking up in the middle of the night several times over with a hungry tummy.
You needn’t worry much. A 2003 report in the Annals of Nutrition and Metabolism decided to test how often participants on fasts would wake throughout the night. The researchers had 13 participants in all, one male and 12 females. All were in good health and not obese.
When the participants fasted for a week, they all lost some weight. More importantly, at least for the sake of sleep, was that they had “a significant decrease in arousals.” In other words, the participants woke up less frequently throughout the night when fasting. Even more promising, the participants’ leg movements while asleep were also reduced.
The study concludes this: “Subjective sleep ratings showed a fasting-induced increase in global quality of sleep, daytime concentration, vigour and emotional balance.”
With fewer nighttime awakenings and fewer leg movements as well, you could certainly sleep longer when fasting. Even if you find your alarm is going off sooner than you’d like, you’ll feel rested and more energetic in the morning so you’re ready to face the day.
Can Fasting Cause Sleep Deprivation?
If you’re normally a poor sleeper, you may have concerns that fasting could only exacerbate that problem, especially for those first few nights of your fast. Is it possible that you could even develop sleep deprivation from fasting?
Sleep deprivation can be caused by schedule changes, stress, illnesses like chronic pain or depression, older age, or having a sleep disorder, including restless leg syndrome or sleep apnea.
Having a bad night of sleep is one thing, but prolonged sleep issues or sleep deprivation can lead to a variety of negative symptoms. These include:
- Reduced coordination and balance
- Boosts in inflammation chemicals and blood pressure, which could heighten your risk of heart disease
- Lowered testosterone levels that can cause poor libido; women may also have lower libido through sleep deprivation
- Changes in brain chemicals that indicate fullness, which could lead to overeating and thus weight gain
- Elevated blood sugar levels that, when prolonged enough, could potentially cause diabetes
- Higher blood pressure if you sleep under five hours nightly
- Weakened immune system that can’t fight off foreign invaders as well
- Drowsiness that can affect work and personal performance
- Moodiness, including being cranky and short with others
- Concentration issues as well as reduced problem-solving abilities and creativity
- Decreases in long-term and short-term memory
Mattress brand Wakefit notes that long-term fasting could interrupt sleep patterns and rapid eye movement or REM sleep. This is the third stage of sleep. The first is when you drift off and are easily woken up for at least 10 minutes after falling asleep. Then you move into the second stage of sleep, which is noted by lower body temperature and a slower heart rate.
Within 90 minutes, you enter REM sleep, which occurs in periods. The first REM period is about 10 minutes in length, but these periods then become longer, sometimes about an hour at a time. Your breathing and heart rate both go up when in REM sleep.
There are associations between less REM sleep and fasting, including this study from 2018 in the Nature and Science of Sleep. To ward off sleep deprivation then, stick to shorter-term intermittent fasts that are about a weeklong at most.
Tips for Falling (and Staying) Asleep on a Fast
You can’t wait until you can eventually fall asleep quickly and sleep better on your fast, but for now, you’re at the beginning of the fast, and you’re struggling. Is there anything you can do to improve your sleep? Try these tips.
Time Your Meals for Less Hunger
If your rumbling stomach is so loud that you can’t get any rest, then you want to be more conscious of your meal timing. If your intermittent fast allows you to eat, try to plan your meal for later in the day. Don’t eat super late into the night, as this can interrupt your blood glucose, but do time your meals so you can end the evening full before retiring to bed for the night.
Avoid Alcohol and Coffee
You shouldn’t consume heavily caloric beverages on a fast anyway, but just in case you need a reminder, please skip the alcohol. Boozy beverages such as beer or wine can make you feel drowsy in the moment, but when the time comes to sleep, you toss and turn.
Coffee has caffeine, which makes it a no-no in the evening. By the way, while black coffee is allowable on most intermittent fasts, it too contains caffeine. Limit your consumption appropriately.
Eat Nutritiously
Make smart eating choices when you can eat during your intermittent fast. A pizza may fill you up in the moment, but it doesn’t have nutrition that will carry you through the long hours of your fast. When you eat fish, nuts, vegetables, fruits, and protein instead, you’re ensuring you’re nourishing your body. You could even have enough satiety that you feel fuller longer, making sleep easier to come by.
Be Comfortable
Making yourself as comfortable as possible may make it easier to fall asleep, even on a fast. The conditions everyone likes when they sleep are different. You might prefer a very cold room while others like it warmer. A white noise machine can drown out nearby sounds so you can relax, and fluffy blankets and pillows will cradle you so you will soon drift off to dreamland.
Stay Hydrated
Consuming water is crucial when fasting, as you lose some of the hydration you normally get from food. Dehydration may contribute to snoring, which can wake you up just when you’re getting into a deep sleep. You may also feel more restless when you’re not hydrated enough, so make sure you nourish yourself with water. Consuming H2O is also a good way to feel fuller even without food, making those sleepless nights rarer.
Conclusion
Fasting can impact sleep for the first few nights, but within three or seven days, your sleep improves. Shorter-term fasts like intermittent fasts can strengthen your circadian rhythm, making it easier to fall asleep. You may also wake up less throughout the night and have fewer instances of leg movements.
Now that you know the ins and outs of sleeping on a fast, you can prioritize getting the rest you need. Best of luck!