Your body does not shut down entirely during sleep. Even in this state of perceived inactivity, the body continues to burn energy to maintain essential life-supporting functions, such as breathing, circulation, and nutrient processing.
This raises an essential question: why is it important to understand nighttime calorie expenditure?
Understanding caloric consumption during sleep is important in determining your Basal Metabolic Rate (BMR). If you’re trying to manage your weight, BMR knowledge is a baseline for regulating how many calories you consume based on your weight goals.
The Science of How We Burn Calories While Sleeping
The body is constantly metabolizing calories, regardless of what you are doing. The total number of calories you burn in 24 hours is known as Total Daily Energy Expenditure (TDEE).
There are three parts to TDEE.
Thermic Effects of Food (TEF)- refers to the energy the body uses to digest, absorb, and metabolize the food we take. It comprises about 10% of your total daily energy expenditure.
Activity-induced energy expenditure (AEE)- 15-35% of your total energy expenditure goes to physical activity, that is, how much you move.
Basal Metabolic Rate-the number of calories your body burns at total rest. This energy expenditure is necessary to sustain the basic functions necessary to keep you alive. These functions include breathing, blood flow, temperature regulation, brain function, and cellular growth and repair.
BMR represents 60%-80% of the TDEE. Basal Metabolic Rate accounts for the highest number of calories burned daily. That’s because the body is constantly burning calories, even when resting and sleeping.
Exactly how many calories do you burn while sleeping?
On average, most people burn 50 calories per hour of sleep. The exact metabolic rate during sleep ranges between 40 and 80 calories an hour, depending on factors such as age, sex, weight, fitness, genetics, metabolic rate, and sleep length, among others.
Basal metabolic rate (BMR) is accurately measured in a lab environment using a special mask called a calorimeter. A calorimeter measures the calories burned by determining the volume of oxygen consumed and carbon dioxide produced. For enhanced accuracy, you will be required to fast for 12 hours and sleep overnight at the lab.
Calorimetry is considered the gold standard in calculating sleep metabolism rate. However, using a mathematical formula it’s possible to approximate how many calories you burn when sleeping.
How to Calculate Your Basal Metabolic Rate During Sleep at Home
Start by estimating your BMR. There are lots of online BMR calculators that will do this for you. Most of them only require you to plug in your gender, height, weight, and age to give you an estimate of your BMR.
However, you can also calculate your BMR on paper using the following formula:
BMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) – (5.677 x age in years)
BMR = 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) – (4.330 x age in years)
The answer you get using an online calculator or the formula above estimates the number of calories you burn while awake in a 24-hour cycle. Divide the answer by 24 to get the hourly rate.
Next, multiply the hourly rate by 85% to get your BMR while asleep. This is because the basal metabolic rate lowers by about 15% during sleep.
Lastly, multiply the result by the number of hours you spend asleep, for instance, 8 hours.
Calorie burned during sleep= BMR/24*0.85*8
Factors Influencing Caloric Expenditure during Sleep
Multiple factors affect nighttime calorie expenditure. These factors include:
Weight and body composition- a person with a larger, fat-free mass typically has a higher BMR because it takes more energy to maintain muscles.
Age- as you age, you tend to lose muscle mass and decrease in activity. These two cause reduced energy requirements, consequently leading to a sluggish metabolism.
Biological sex- men are generally larger and more muscular than women. Thus, they tend to burn more calories at rest than women.
Genes- the genetic makeup you inherited from your parents also influences calorie burning.
Experts have yet to understand the complex relationship between sleep and weight management.
On the one hand, it’s believed that metabolism decrease by 15% when sleeping. However, it’s also clear that sleep quality also directly impacts weight management by influencing:
Appetite- sleep deprivation increases appetite-increasing hormones (ghrelin) and lowers the level of satiety hormones (leptin), leading to increased hunger.
Choice of food- lack of sleep is associated with increased cravings for foods higher in fat, sodium, and added sugar, all of which can lead to weight gain.
Motivation to participate in physical activities- restful sleep promotes physical activity by promoting muscle growth and recovery. Another importance of deep sleep for calorie burning is waking up feeling energized and motivated to exercise.
We believe you now understand how sleep affects metabolism. Research shows that besides your age, gender, genetic makeup, and weight, deep sleep has a central role in metabolism and weight management.
If you’re trying to lose weight, begin by understanding your basal metabolic rate during sleep and explore ways to enhance it. Next, recognize that sleep influences all other factors that affect weight management, including appetite, food choices, muscle recovery, and the motivation to exercise.
Lastly, remember that reaping the benefits of sleep for weight loss comes down to sleep quality, not quantity. Restorative and comfortable sleep starts with a conducive sleep environment. Strive to optimize your bedroom for sleep by minimizing light sources, blocking disruptive background noises, and investing in comfortable bedding materials.