How many calories do we burn while sleeping? Many people are surprised when they find out how many calories we burn while we sleep.
Although sleep requires a lot less energy than most daily activities, it is still an active period for our brain and some other bodily functions.
The exact number of calories burned while sleeping depends on a complex interplay between sleep, diet, exercise, and other variables. If you're struggling with weight management or energy levels, understanding the factors that affect your metabolism can help you regain control of your health.
How many calories do we burn while sleeping?
As a rough estimate, we burn about 50 calories per hour1 while we sleep. However, each person burns a different amount of calories during sleep, depending on their personal basal metabolic rate2 (BMR).
Basal metabolic rate refers to the energy required for basic functions such as respiration, circulation, temperature regulation, and cell growth and repair.
In most people, basal metabolic rate accounts for about 80%3 of the total calories burned in a day. The brain itself burns glucose4 for energy, accounting for about 20% of the calories we consume when we are at rest.
Sleep is a period of restoration and regeneration of the body5. To do this more efficiently, our body temperature drops, our breathing slows down and our metabolism slows down.
On average, most people burn about 15% fewer calories while they sleep, compared to their basal metabolic rate during the day.
What Factors Affect Basal Metabolic Rate?
Basal metabolic rate varies from person to person depending on several factors, only some of which can be changed:
- Height and weight: The bigger a person's body is, the more calories it needs to function.
- Fitness: Muscle burns more calories than fat, so people who are fit and regularly active burn more calories, even when they are at rest.
- Sex: Men generally have a higher BMR than women because they tend to have a higher rate of repair and regeneration.
- Age: Growing children have a higher metabolism, but metabolic needs decrease as we age.
- Diet: Sticking to a healthy diet can help manage body fat composition.
- Sleep quality: Poor sleep quality and insufficient sleep have a detrimental effect on metabolism.
- Race: Some studies show that African Americans may have a naturally lower BMR.
Genetics. Genetics can affect metabolism to some extent.
- Hormones and medical conditions: Pregnancy, lactation, menopause, hypothyroidism or hyperthyroidism, and other conditions can increase or decrease the basal metabolic rate. Consult your doctor if you think an underlying condition could be affecting your metabolism. How many calories do we burn while sleeping?
How to calculate the calories you burn while you sleep
Calculating your exact basal metabolic rate requires the use of a calorimeter7. A calorimeter measures the amount of energy you use by analyzing the oxygen and carbon dioxide that is inhaled and expelled from your body.
Typically, people who want the most accurate reading of their basal metabolism spend the night in a lab, abstain from exercise for 24 hours, fast for 12 hours, and sleep for at least 8 hours before the reading.
These details are important because digestion and exercise are energy-demanding processes that cause spikes in metabolism. Measurements are then performed in the morning in a dark, temperature-controlled setup.
Due to the expensive and complex nature of this test, it is impractical for the average person to perform. However, you can get a general idea of your basal metabolic rate using one of several equations. One of the most common is the Harris-Benedict8 equation, which is based on weight, height, age and sex:
Male: BMR = 66.5 + (13.8 x weight in kg) + (5 x height in cm) – (6.8 x age in years)
Female: BMR = 655 + (9.6 x weight in kg) + (1.8 x height in cm) – (4.7 x age in years)
The result gives you your basal metabolic rate while you are awake for a 24-hour period. To estimate approximately how many calories you burn per hour of sleep, divide the number by 24 to get the hourly rate, then multiply by 0.85 to calculate your lowest metabolic rate during sleep.
Although it differentiates between men and women, the Harris-Benedict equation does not take into account genetics, race, hormones, muscle-to-fat ratio, or medical conditions. To get a general idea of your muscle to fat ratio, you can calculate the Harris-Benedict equation9 (BMI):
BMI = weight (lbs) / [height (in)] 2 x 703
A BMI below 18.5 is considered underweight and a BMI above 25 is considered overweight. However, for Asian or Asian American ethnicity, a BMI over 22.9 is considered overweight. In general, overweight people have a higher percentage of body fat, which burns fewer calories than muscle. Please note that this BMI formula may not be accurate for pregnant women, bodybuilders or other people who have an atypical body composition.
Can you increase the number of calories you burn while sleeping?
To increase the number of calories you burn while you sleep, you need to increase your basal metabolic rate. The easiest way to do this is to eat right, get enough exercise and sleep well. How many calories do we burn while sleeping?
Since we burn more calories when we're awake, it's not surprising that skipping a night of sleep causes us to temporarily burn more calories10. However, in the long term, significant research has shown that chronic lack of sleep is linked to obesity. Lack of sleep causes an increase in the hormone11 that makes you crave high-calorie foods.
Sleep loss also increases cortisol levels, which affects your body's ability to regulate glucose and can contribute to weight gain, insulin resistance, and even type 2 diabetes. And while the extra time awake can have as a result of burning more calories, restricting calories while lacking sleep causes the body to burn lean mass instead of fat.
Since the brain burns more calories during REM sleep, sleep interruptions that affect the time spent in this stage can have an impact on the calories you burn. Adopting good sleep hygiene habits and creating a cool, dark, quiet bedroom environment can encourage your body to naturally cycle through the stages of sleep and optimize your metabolism while you sleep.
The link between healthy sleep and metabolism is clearly seen in people with obstructive sleep apnea (OSA), a sleep disorder that causes fragmented sleep due to repeated delays in breathing. Obesity and OSA often go hand in hand, suggesting that one condition can exacerbate the other.
Exercise, diet and sleep
Some studies have found that eating too close to bedtime12 can lead to weight gain, although a more important factor seems to be the type of food you eat. If you feel compelled to indulge in a midnight snack, stay away from junk food and opt for a light and healthy snack. As a bonus, a healthier diet, in turn, improves sleep quality.
Regular exercise and a healthy diet can help regulate your sleep schedule, improve your muscle-to-fat ratio, and boost your metabolism. Avoid drinking caffeine and alcohol before bed. While caffeine causes a temporary spike in metabolism, it interferes with sleep and is not an effective weight loss strategy.