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After a long day, there’s no better feeling than hopping into bed and going to sleep. It’s a time to rest (obviously), but there’s actually a lot that happens in your body while you snooze. Beyond recharging your body and mind and potentially decreasing the risk of cardiovascular disease, diabetes, and cancer, per a 2021 study in the Journal of Clinical Sleep Medicine, sleep actually burns some calories too.
“While we sleep, our bodies are actually hard at work,” says David Rosen, MD, a sleep medicine doctor and medical director at Complete Sleep. “Sleep is the time when the body is busy repairing and growing new cells. Plus, your brain—which uses about 20 percent of your caloric needs—stays active even during sleep to maintain a level of consciousness.” Think: Responding to important stimuli (like your morning alarm clock, a baby crying, or a fire alarm sounding) or dreaming during REM sleep stages.
Now that you know your body burns calories when sleeping, it’s only natural to wonder, how many? We spoke with doctors to determine how to calculate exactly how many calories you burn when sleeping.
Meet the experts: David Rosen, MD, is a sleep medicine doctor and medical director at Complete Sleep. Susan Savery, MD, is an obesity medicine and primary care physician at PlushCare.
Here’s how your body uses calories while you sleep.
According to Susan Savery, MD, an obesity medicine and primary care physician at PlushCare, a person tends to burn on average 40 to 60 calories per hour while sleeping. So, if you sleep a full eight hours, that’s between 320 and 480 calories. “However, this number varies based on your weight, age, gender, body composition, and overall health,” she says.
To put this into perspective, you actually burn similar amounts of calories sleeping as you do sitting down. “They both burn around 40 to 60 calories per hour whereas standing requires more calories, burning around 80-120 calories per hour,” Dr. Rosen says.
As for what your body is using that energy for during the night? The answer is simple: keeping you alive and functioning.
“Even during sleep, your body continues essential functions that require energy: your heart pumps, your lungs breathe, your brain maintains activity, and your cells repair and regenerate,” Dr. Rosen says. “Your organs need energy to function, and processes like digestion and tissue repair are actually more active during sleep.” The amount of calories required to keep all this going is commonly referred to as your basal metabolic rate (BMR). Approximately 70 to 80 percent of calories burned are used up by your BMR.
And, BTW, you burn different amounts of calories during the various sleep stages.
“REM sleep burns more calories than non-REM sleep because the brain is highly active, almost as active as when awake,” Dr. Rosen says. Meanwhile, deep sleep burns fewer calories because your body temperature and heart rate decrease, therefore using less energy. As you cycle between these stages, the exact amount of calories you burn fluctuates, he says.
How To Calculate How Many Calories You Burn While Sleeping
Not satisfied with the general 40 to 60 calories per hour calculation? You can get even more granular about how many calories you burn while sleeping by including factors like height, weight, age, and basal metabolic rate.
First, calculate your BMR.
To calculate your BMR, Dr. Savery suggests using the Mifflin-St. Jeor Formula:
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For women: BMR = (4.536 x weight in pounds) + (15.88 x height in in) – (5 x age in years) – 161
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For men: BMR = (4.536 x weight in pounds) + (15.88 x height in inches) – (5 x age in years) + 5
Now, you’re ready to figure out how many calories you burn during sleep.
Dr. Savery recommends the following formula:
(BMR/24) x (numbers of hours slept) x (0.85)
This equation accounts for your basal metabolic rate divided by 24 (which represents the number of hours in a day), the number of hours slept, and the percentage of the basal metabolic rate that sleep accounts for (85 percent).
These Factors Might Affect How Many Calories You Burn In Your Sleep
Age: As you get older, your BMR naturally slows, which means that you’ll burn fewer calories while you snooze. “This is especially noticeable in women during perimenopause and menopause, when decreasing estrogen levels cause our metabolism to slow down,” Dr. Savery says.
Weight: Your body weight also plays a role in how many calories you need while sleeping. The larger a person’s body is, the more calories their body needs to spend in order to keep them functioning properly,” Dr. Savery says. So, those with more weight will burn more calories while they sleep.
Body composition: Muscles are a calorie-burning powerhouse. “The more muscle you have, the more calories you will burn during sleep,” according to Dr. Savery. Here’s why: Muscle tissue requires constant energy for maintenance even during sleep, while fat tissue requires very little energy to maintain which is why someone with muscle will burn more calories while both at rest and active, says Dr. Rosen.
Tips To Help You Snooze Better In The First Place
At the end of the day, sleep is important for overall health and well-being so you want to make sure you’re prioritizing it and getting some quality shut-eye. You’ve probably heard these tips before, but just to make sure you have your bases covered, Dr. Rosen offers these tips to help improve your sleep hygiene:
Prioritize a consistent sleep schedule: Going to bed and waking up at the same time everyday can have a positive impact on your overall sleep because it helps regulate your circadian rhythm. It might seem tempting to go to bed late and sleep in on the weekends, but if you can keep your sleep schedule consistent, you’ll be better off in the long run.
Don’t use your phone before bed: Although watching TikTok or scrolling through Instagram before bed is fun, you’ll want to put your phone away at least an hour before you plan to sleep. Blue light from screens suppresses melatonin, a hormone produced by the brain that affects the body’s sleep-wake cycle. Essentially, the blue light from your phone screen can hinder melatonin production and keep you from catching those Zzzs.
Have a comfortable sleep environment: Set yourself up for success by creating a comfortable sleep environment at night. This may involve keeping the temperature cool, using a sleep mask to block out light, and wearing ear plugs to cancel out noise.
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