When we think about burning calories, most of us think about lifting weights or a long sweaty run. But did you know your body is always burning calories, even when you’re fast asleep?
Your body has to burn a set number of calories to keep you breathing, your heart beating, and your digestion working.
Below, we’ll share how many calories you burn while asleep, and how you can burn more calories each day all through getting the right amount of sleep for you at the right times for your body clock.
The short answer is yes, you do burn calories, even when you sleep. As a rough idea, you’ll burn about 50 calories an hour while sleeping.
But the exact number of calories a person burns will all depend on their basal metabolic rate (BMR), or how many calories your body burns to do essential tasks like:
It’s thought your BMR is about 15% lower during sleep compared to when resting during the day.
Your basal metabolic rate is determined by factors like:
Working out your BMR is a complicated process. It involves measuring how much oxygen you breathe in and carbon dioxide you breathe out, and you usually do the test in a lab after fasting for 12 hours and sleeping for eight hours.
As a result, you usually can’t measure your BMR yourself. What you can do, however, is measure your resting metabolic rate (RMR).
This is how many calories you burn while completely at rest, and it will give you a rough idea of your BMR. Here’s how you can work out your RMR:
Revised Harris-Benedict BMR equation:
Mifflin-St Jeor equation:
But remember, these equations aren’t 100% accurate.
Our sleep looks very different throughout the night. A normal night of sleep should look something like this:
Once you’ve moved through all four stages of sleep, you’ll have completed one sleep cycle. This could last from 70 to 120 minutes. You’ll then begin another cycle from the start.
When it comes to calories, REM burns the most as your heart rate and brain activity are higher compared to the other non-REM stages. In fact, using just electrical brainwave activity, it’s often impossible to tell brain activity during REM sleep apart from brain activity while awake.
During deep sleep, on the other hand, your heart rate, brain activity, and body temperature are lowest, so you need less energy, and therefore you burn the fewest calories during this sleep stage.
To burn more calories in your sleep you’d have to increase your BMR. You can do this by putting on more muscle (muscle burns more calories than fat, even when resting) or eating more protein (it takes more calories to digest protein than it does fat or carbohydrates).
However, these things aren’t really going to help you make a significant difference to your weight. But you can still use the power of a good night’s sleep to help your waistline.
You can learn more about the link between sleep and weight loss here. To summarize, you can put on weight and struggle to lose weight if you:
Here’s how to make sure that doesn’t happen.
Sleep debt is the measure of how much sleep you owe your body. This is compared against your sleep need, the genetically determined number of hours of sleep you need.
One study suggests the average sleep need is 8 hours 40 minutes, plus or minus 10 minutes or so, but 13.5% of the population may need 9 hours or more sleep a night.
When you don’t meet your sleep need, you start building up sleep debt. And this can mess with your hunger hormones, glucose metabolism, and your self-control. Plus, when you don’t get enough sleep, your levels of the stress hormone cortisol increase. This can lead to you storing more body fat, especially around the belly.
So, it’s easy to overeat and your body starts storing more fat, all because of a lack of sleep each night.
When it comes to calories, one study found people ate 385 more calories after a night of partial sleep deprivation. But the amount of calories they burned didn’t change.
In fact, you may eat extra calories when tired and burn fewer as you’ll feel low on energy and have less motivation to go to the gym, or do much physical activity at all.
You can reverse this trend, though. Research shows your resting metabolic rate is lower after sleep deprivation, but it increases back to previous levels when you get enough sleep. And a 2022 study found when participants increased their sleep duration by about 1.2 hours a night, they ate about 270 fewer calories during the day.
You can use the RISE app to find out your individual sleep need and how much sleep debt you’re carrying. We recommend keeping this below five hours to maximize your energy levels, and weight loss, each day.
If you have high sleep debt, you can pay it down by:
RISE users on iOS 1.202 and above can click here to view their sleep need.
RISE users on iOS 1.202 and above can click here to view their sleep debt.
Beyond getting enough sleep each night, you need to get this sleep at the right time for your circadian rhythm.
Your circadian rhythm is the roughly 24-hour cycle of your biological clock. It dictates things like your sleep-wake cycle, when your body produces certain hormones, and when your body temperature fluctuates.
You might be out of sync with your circadian rhythm if:
Beyond your sleeping habits, you can also mess up your body clock through ill-timed meals and exercise. That’s because you have more than one circadian rhythm. There’s one master clock in your brain and other body clocks, called peripheral clocks, located in almost every tissue and organ system, including your immune system and digestive system.
A zeitgeber is something that can change the timing of your circadian rhythm. Light is the most powerful zeitgeber, but meals and exercise also have this effect, especially on your peripheral clocks.
So, eating when your body isn’t expecting you to — such as late in the evening or at irregular times — will cause your peripheral clocks to become out of sync with your master clock.
When you are out of sync, either through badly timed sleep or meals:
You can live in sync with your circadian rhythm by:
The RISE app can predict your circadian rhythm each day so you can see when your body naturally wants to wind down for bed and go to sleep. You can then avoid meals and workouts at this time, and schedule your bedtime to match.
RISE users on iOS 1.202 and above can click here to see their upcoming energy peaks and dips on the Energy screen.
Heads-up: Avoid supplements that promise to speed up calorie burning in your sleep. Not only are they most likely ineffective and could come with dangerous side effects, they may also contain stimulants like caffeine that will interfere with your sleep. And as we’ve shown, you need to prioritize sleep to lose or maintain weight.
You can learn more about the best way to lose weight here.
The bottom line is you do burn calories in your sleep, but that isn’t the reason sleep is so important for weight loss. Research shows when you don’t get enough shut-eye or stay in sync with your circadian rhythm, you’ll eat more calories and burn fewer calories, upping your odds of weight gain.
To burn more calories with your sleep, use the RISE app to find out your individual sleep need and strive for this each night. Keep sleep debt low and sync up your sleep, meals, and exercise to your circadian rhythm. RISE can also guide you through 20+ sleep hygiene habits to make falling asleep, meeting your sleep need, and staying in sync with your circadian rhythm easier.
You burn calories when you sleep as part of your basal metabolic rate (BMR). This is the calories your body needs to burn to do basic functions like breathing and keeping your heart beating and your digestion going. We burn roughly 50 calories an hour while asleep, but the exact number depends on your BMR.
You burn more calories awake in bed compared to being asleep. It’s thought your basal metabolic rate, the amount of calories you burn just to do basic functions, is 15% lower when asleep than when awake resting.
You may not burn much fat in your sleep, but that doesn’t mean sleep isn’t integral to weight loss. When you don’t get enough sleep at the right times for your body clock, research shows you eat more calories, burn fewer calories, and store more fat. Not getting enough sleep has been linked to obesity and abdominal obesity.
While you don’t want hunger keeping you up, you also want to avoid late-night eating as it can mess up your body clock, impact your sleep, and cause weight gain. If you can’t fall asleep due to hunger, eat a light, healthy snack.
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