Burn calories while you sleep! It might sound like a gimmick from the latest quick-fix diet plan, but the idea of burning calories during sleep isn’t just sensationalism—it’s science. You really do burn calories while sleeping, and quite a few at that! However, before you ditch your yoga mat for the bed, here are a few things you should know.
How Many Calories Do You Burn While Sleeping?
As with many questions related to weight loss and metabolism, the answer is, “It depends.”
Each person has a unique Basal Metabolic Rate (BMR), also known as resting metabolic rate. “BMR is the minimum amount of energy or calories your body needs to sustain basic life functions,” explains Danielle Gaffen, MS, RDN. “It reflects the amount of energy your body uses over 24 hours while at complete physical and mental rest.”
BMR includes essential functions like breathing and blood circulation and is influenced by factors such as weight, height, body composition, age, biological sex, and activity level.
BMR accounts for roughly 60% of your total energy expenditure, with the remaining 40% coming from digesting food, daily activities, and exercise. To determine how many calories you burn while sleeping, you’ll need to look at your BMR.
How to Calculate Calories Burned During Sleep
To estimate the calories burned during sleep, multiply your BMR by the number of hours you sleep. According to Gaffen, the most accurate way to determine BMR is through direct or indirect calorimetry, which measures heat production or gas exchange. However, this method requires expensive equipment and is rarely accessible.
A more practical approach is using the Mifflin-St. Jeor equation, which, as per one study, estimates BMR within 10% of the actual value. Here’s how it’s calculated:
Men: 10 × weight (kg) + 6.25 × height (cm) – 5 × age (years) + 5
Women: 10 × weight (kg) + 6.25 × height (cm) – 5 × age (years) – 161
Curious about your total daily calorie burn? “Online calculators can estimate the number of calories your body burns in a day by factoring in your weight, gender, age, height, and activity level,” says Gaffen. She recommends tools like the Body Weight Planner from the National Institutes of Health or the MyPlate Plan widget from the USDA.
However, for the most accurate assessment, consulting a registered dietitian is your best bet.
Can You Influence How Many Calories You Burn?
Many factors that determine your BMR, and thus your calorie burn during sleep, are beyond your control. However, building muscle mass can make a small difference, as muscle burns more calories than fat. That said, research suggests that gaining muscle mass may not significantly boost calorie burn.
In one study, previously sedentary women who completed six weeks of resistance training saw a noticeable increase in their BMR. However, none of the participants experienced significant weight loss or changes in body composition.
If your goal is to burn more calories, focusing on your activity level while awake is more effective. Incorporate regular exercise and aim to stay active throughout the day—whether it’s running errands on foot, taking the stairs, or swapping a seated meeting for a walking one.
Does Eating Before Bed Affect Calorie Burn?
Digesting food burns calories, so eating before bed can temporarily increase your energy expenditure. However, eating at night is unlikely to boost (or sabotage) your weight loss efforts.
“It’s not so much about when you eat as it is about how much you eat,” says Gaffen. An apple has the same number of calories whether eaten for breakfast or at midnight.
That said, the timing of meals can affect eating behaviors. “It’s common to engage in mindless snacking in the evening while relaxing or watching TV,” Gaffen explains. “This habit can lead to overeating and potential weight gain. If you’re prone to nighttime snacking, pay attention to portion sizes and choose healthier options.”
