I’ve seen this question asked so often, “Does Sleeping Count as Fasting?”
Let’s face facts, fasting and intermittent fasting is tough.
Plus, there seems to be various rules, depending on which specific intermittent fasting diet you follow.
However, should you include sleep as part of your fasting window?
Or are you supposed to be fasting during your waking hours in order for it to count?
Let’s find out.
Does Sleeping Count as Fasting?
Yes, sleeping does count as fasting. In fact, you should be using sleep as a way to make intermittent fasting easier. You’ll generally need to go without any food for at least 12 hours for it to be considered a fast. So, it makes perfect sense that some or most of these hours are spent sleeping. That being said, the more popular forms of intermittent fasting, e.g. 16:8, 20:4, or 24 hours, will usually require you to sleep through some of your fasting window anyway.
1. Can You Sleep While Intermittent Fasting?
Firstly, I think it’s important to state that sleeping should form part of your fasting window.
Let’s face facts, fasting and intermittent fasting is tough.
So, anything that can help you along the way is a bonus.
In reality, for a fast to actually be considered a fast, you’ll typically need to go at least 12 hours without consuming any calories.
That being said, this can vary from person-to-person, as our body’s generally react differently to each other.
However, 12 hours is a good starting point for most people.
Now, I would hazard a guess that you don’t actually sleep for a full 12 hours, although this isn’t totally unheard-of.
But, in truth, as a healthy adult, you should be getting approximately 7-9 hours of sleep a night, which is usually converted to 8 hours for a good night’s sleep.
This means that you realistically only need to fast for another 4 hours in order to hit the magical 12 hours.
So, in effect, the easiest way to achieve this would be to fast for two hours before you go to sleep and then fast for another two hours when you wake up in the morning.
The Most Popular Forms of Intermittent Fasting
However, there are obviously quite a few variations of intermittent fasting, and most of the more popular diets require you to fast for longer than 12 hours.
In fact, the most popular intermittent fasting diets typically require you to fast for 16, 20 or 24 hours.
This should tell you just how important sleep is during your fasting window.
Essentially, it would actually be impossible to fast for 16, 20, or 24 hours without including sleep as part of your fasting window.
Well, I guess you could, but you wouldn’t be getting much sleep, once you include your fasting window, and the time it takes to prepare food, eat, wash up, etc.
Plus, even though you’re asleep, your body will react in exactly the same way as if you fast while awake.
So, you are still burning calories through breathing, moving, and your vital organs functioning.
Your body will usually use glycogen stores for energy, whether you’re awake or asleep.
However, the whole point of intermittent fasting is for your body to eventually convert to burning fat stores for energy.
This is how you lose weight and burn body fat, as your body is now using ketones to fuel brain and body activity.
So, without a doubt, you should always include sleep as part of your fasting window.
2. Does Intermittent Fasting Cause Sleep Issues?
Okay, so we’ve established that it’s absolutely fine to count sleep as part of your fasting window.
However, I now want to look at things the other way around, i.e. what effect intermittent fasting has on sleep.
Now, you’ll generally hear that intermittent fasting leads to better quality sleep.
Basically, it is said that intermittent fasting reinforces and improves your circadian rhythms.
Your circadian rhythms are responsible for a whole series of biological functions.
However, they are most commonly associated with your metabolism, appetite, and your sleep-wake cycle.
This is simply another way of saying that your circadian rhythms will tell your brain and body when it’s time to sleep and when it’s time to be awake.
Admittedly, circadian rhythm primarily functions through sunlight, which also explains why we’re usually awake when it’s light and asleep when it’s dark.
Something else to consider is that the Human Growth Hormone is usually secreted while we sleep.
This is generally during the second phase of deep sleep.
And it is the Human Growth Hormone that is responsible for restoring muscles, the cells of the body repairing themselves, as well as burning fat.
So realistically, if you’re not getting a good night’s sleep, this could also explain why you aren’t gaining muscle or you’re putting on weight.
However, as intermittent fasting regulates circadian rhythms, it should help you get a fantastic night’s sleep, which is also great for your overall health and body composition.
The Downside to Intermittent Fasting & Sleep
So, no doubt, this all sounds fantastic, and as though intermittent fasting actually helps you to sleep better.
Now, while this is true in most cases, there are also various sleep issues that can be caused by intermittent fasting.
And the most common of these is insomnia.
There are various reasons why intermittent fasting can cause insomnia, so it’s something you definitely need to be aware of.
The most common reason for insomnia will have to do with the timing of your meals, especially if you’re eating at night.
Firstly, whenever you eat your body temperature rises, as you’re using energy to consume your meal.
This is actually the opposite of what’s required to fall asleep, as our core temperature tends to drop ever so slightly.
Furthermore, if you eat a heavy meal just before bed, which is highly likely if you’ve been fasting for a set period, this can cause digestive issues.
I’m sure you’ve had many a night in the past when you can’t sleep simply because you’re stuffed.
Finally, excessive fasting, as well as eating a meal close to bedtime, can conflict with the hormone melatonin.
This is the sleep hormone, which works in conjunction with your circadian rhythms.
So, while intermittent fasting is generally viewed as being good for sleep, you do need to be aware of the potential issues with sleep it can cause too.
Circadian Rhythm – What is It? How Does it Work? & More
So, I hope you understand that sleep does count as fasting.
In fact, I would always advise that sleep should form part of your fasting window.
You’ll generally need to fast for a minimum of 12 hours for it to be considered a fast.
However, the most popular forms of intermittent fasting require you to fast for 16, 20, or 24 hours.
That being the case, it would be very difficult, if not impossible, to fast for these specific periods of time without including sleep as part of your fasting window.
Hi, I’m Partha, owner and founder of My Bodyweight Exercises. I am a Level 3 Personal Trainer and Certified Strength & Conditioning Specialist through the Register of Exercise Professionals, United Kingdom. I have been a regular gym-goer since 2000 and coaching clients since 2012. My aim is to help you achieve your body composition goals.