Even when resting and sleeping, the body requires a constant source of energy to maintain a wide range of metabolic processes.
Many different factors influence metabolism, which can make it difficult to calculate accurately how many calories a person burns during sleep. However, by estimating a person’s basal metabolic rate (BMR), it is possible to come up with an approximate figure.
In this article, we discuss what BMR is, how to calculate it, and how to use the result to estimate the number of calories that a person burns while sleeping. We also provide some sleep hygiene tips.
What is BMR?
It is essential for the body to use energy continuously for maintenance and to function correctly. Although the body burns some of its calories through physical activity, basal metabolism accounts for around 80% of all energy expenditure.
Basal metabolism refers to all of the processes that keep the body alive, functioning, and healthy. These include:
- blood circulation
- cellular growth and repair
- brain and nerve function
- temperature control
These metabolic processes require a constant supply of energy, so the body is always burning calories, even when a person is resting or sleeping.
BMR is the number of calories that the body burns every 24 hours due to basal metabolism. Essentially, it is how many calories a person would use in a day if they just rested and did no physical activity.
Many different factors affect BMR, including age, body size, sex, and genetics. For this reason, everyone’s BMR is different.
To determine how many calories the body burns during sleep, it is first necessary to calculate the BMR. This calculation is not straightforward because many factors influence BMR.
Accurately measuring BMR requires using special equipment to determine how much oxygen a person is breathing in and out over a specified period.
However, it is possible to estimate BMR using the Harris-Benedict equation, which takes into account a person’s sex, height, weight, and age.
For females, the formula is:
BMR = 665.1 + (4.34 x weight in pounds) + (4.7 x height in inches) – (4.68 x age in years)
For males, the formula is:
BMR = 66.47 + (6.24 x weight in pounds) + (12.71 x height in inches) – (6.78 x age in years)
These formulae will give the number of calories that the body will burn over a whole day due to its BMR alone.
For example, a 40-year-old male who weighs 195 pounds (lb) and is 5 feet (ft) 9 inches (in) tall would have an approximate BMR of 1,889 calories per day:
BMR = 66.47 + (6.24 x 195) + (12.71 x 69) – (6.78 x 40)
BMR = 66.47 + 1,216.8 + 877.0 – 271.2
BMR = 1,889.07 calories per day
A 50-year-old female who weighs 160 lb and is 5 ft 4 in tall would have an approximate BMR of 1,426 calories per day:
BMR = 665.1 + (4.34 x 160) + (4.7 x 64) – (4.68 x 50)
BMR = 665.1 + 694.4 + 300.8 – 234
BMR = 1,426.3 calories per day
Calculating calories burned while sleeping
The body continues to burn calories throughout the night to support its metabolic processes. However, because the body is physically inactive, the metabolic rate is around 15% lower when a person is asleep than when they are awake.
To estimate how many calories the body burns during sleep, a person needs to calculate their hourly BMR and multiply that by the number of hours that they sleep before reducing the figure by 15%.
They can do this using the following formula:
Calories burned while sleeping = (BMR / 24) x number of hours asleep x 0.85
The 40-year-old male who weighs 195 lb and is 5 ft 9 in will burn approximately 535 calories during an 8-hour sleep:
Calories burned asleep = (1889.07 / 24) x 8 x 0.85
Calories burned asleep = 78.71 x 8 x 0.85
Calories burned asleep = 629.68 x 0.85
Calories burned asleep = 535.23 calories
The 50-year-old female who weighs 160 lb and is 5 ft 4 in will burn approximately 404 calories during an 8-hour sleep.
Calories burned asleep = (1426.3 / 24) x 8 x 0.85
Calories burned asleep = 59.43 x 8 x 0.85
Calories burned asleep = 475.43 x 0.85
Calories burned asleep = 404.12 calories
It is important to remember that these calculations provide only a rough estimate of BMR and calories burned while sleeping.
Factors that affect BMR
Height and weight can influence BMR.
A range of factors can influence a person’s BMR. These include:
- ethnicity and race
- height and weight
- hormone levels
- muscle-to-fat ratio
- physical activity levels
- amount and quality of sleep
- pregnancy and lactation
- general health
- health conditions that affect the metabolism, such as hypothyroidism and hyperthyroidism
Sleep hygiene tips
Getting enough sleep is vital to a person’s physical and mental health. Both the amount of sleep and its quality are important. Not getting enough quality sleep can affect a person’s energy levels, mood, concentration, and work performance.
According to the National Institute of Neurological Disorders and Stroke, research shows that inadequate sleep can also increase a person’s risk of several health conditions, including:
The American Academy of Sleep Medicine and the Sleep Research Society recommend that people between the ages of 18 and 60 years get at least 7 hours of sleep every night.
Some tips that can help improve a person’s quality of sleep include:
- avoiding caffeine or other stimulants in the hours before bedtime
- going to sleep and waking up at the same time each day
- getting regular exercise
- ensuring that the bedroom environment is dark, comfortable, and cool
- waking up to natural light
- doing something relaxing before bed, such as reading a book or taking a warm bath
Even when resting or asleep, the body is constantly burning calories to sustain a range of vital bodily functions, which we refer to collectively as the basal metabolism. Basal metabolism incorporates all of the processes that keep the body alive, functioning, and healthy, such as breathing, blood circulation, and brain function.
BMR is the number of calories that the body burns each day due to basal metabolism. BMR depends on a variety of factors, such as age, body size, and genetics. As a result, everyone’s BMR will be different.
A person can estimate their daily BMR using a formula that takes into account their sex, age, weight, and height. Using this BMR value, it is possible to estimate how many calories the individual burns while sleeping.