The human body constantly expends energy, even during deep rest. Calorie burning does not stop during sleep because the body must continue performing life-sustaining functions like breathing, circulating blood, and regulating temperature. On average, an adult burns approximately 40 to 55 calories per hour while sleeping. This nightly energy expenditure is determined by your Basal Metabolic Rate (BMR).
How Basal Metabolic Rate Determines the Number
The Basal Metabolic Rate represents the number of calories your body burns over a 24-hour period to keep your organs functioning at rest. This rate accounts for the energy used by the heart, lungs, brain, and other vital systems when you are in a completely sedentary state. While BMR is typically measured in a perfectly rested and fasted state, it serves as the foundational figure for estimating sleep calorie burn.
To approximate the calories burned during sleep, you first calculate your total daily BMR and then divide that number by 24 hours to find your hourly rate. Since metabolic activity slows slightly during sleep, your actual burn rate is about 15% lower than your awake BMR. For a rough example, a person weighing 150 pounds (about 68 kilograms) burns approximately 46 calories every hour while sleeping, totaling around 368 calories over an eight-hour night.
This calculation highlights that the higher your BMR, the more calories you will burn while asleep. A simple way to estimate your hourly sleep burn is to multiply your body weight in pounds by 0.42. For instance, a person weighing 180 pounds would burn about 75.6 calories per hour.
Key Factors That Change Your Sleep Calorie Burn
Several individual characteristics modify the BMR calculation and affect the precise number of calories burned during the night.
Body Weight and Composition
Body weight is a primary factor, as a heavier body requires more energy for basic functions like supporting the mass and circulating blood, resulting in a higher caloric expenditure. Body composition also plays a role because muscle tissue consumes more energy than fat tissue, even at rest.
Age and Sex
Age influences the process, as metabolism naturally slows down over the lifespan, meaning older adults burn fewer calories during sleep than younger adults. Men generally have a higher BMR than women due to greater average muscle mass.
Sleep Duration and Environment
Sleep duration is a factor, as sleeping for an extra hour directly increases the total number of calories burned overnight. Environmental conditions, particularly ambient bedroom temperature, can also impact the burn rate. Sleeping in a cooler environment may cause the body to expend extra energy to maintain its core temperature, slightly elevating calorie consumption.
Why Quality Sleep Matters for Overall Metabolism
While the number of calories burned during sleep is relatively fixed, sleep quality has a greater long-term impact on overall metabolic health and weight management. Poor or insufficient sleep disrupts the balance of hormones that regulate appetite and energy balance. The two primary hormones affected are leptin and ghrelin.
Leptin is the satiety hormone that signals fullness, while ghrelin is the hunger hormone that stimulates appetite. When sleep is restricted, leptin levels decrease and ghrelin levels increase, creating a hormonal environment that encourages eating. This imbalance leads to increased hunger and a stronger drive to consume more calories the following day.
The resulting increase in caloric intake easily outweighs any minimal increase in calories burned from acute sleep deprivation. A lack of quality rest can undermine weight management efforts by altering the body’s system of energy regulation. Prioritizing sufficient, high-quality sleep is a meaningful strategy for supporting a healthy metabolism.