Burn calories while you sleep! It sounds like a bogus claim designed to rope you into the latest quick-fix diet program. However, the concept of burning calories while sleeping isn’t sensationalism — it’s science. You do burn calories while sleeping. Quite a few, actually. But before you trade in your yoga mat for a cot, there are a few things you should know.

How Many Calories Do You Burn Sleeping?

So, just how many calories do you burn sleeping? As with so many questions related to weight loss and metabolism, the answer is: “It depends.”

Each of us has a unique basal metabolic rate (BMR), or resting metabolic rate. “Basal metabolic rate is the minimum amount of energy, or calories, expended that is compatible with sustaining life,” says Danielle Gaffen, MS, RDN. “An individual’s BMR reflects the amount of energy used during 24 hours while physically and mentally at rest.”

BMR encompasses basic bodily functions, like breathing and blood circulation. It’s determined by factors including weight, height, body composition, age, biological sex, and activity levels.

Essentially, BMR is your calorie-burning baseline that accounts for approximately 60 percent of your total energy expenditure, with the remaining 40 percent coming from digesting food, performing everyday activities, and exercising. If you want to know how many calories you burn sleeping, look to your BMR.

How Do You Calculate How Many Calories You Burn During Sleep?

Calculating how many calories you burn sleeping is a matter of multiplying your BMR by the number of hours you’re asleep. Gaffen explains that the most accurate method for determining your BMR is through direct or indirect calorimetry, a technique that measures the subject’s heat production or gas exchange. Calorimetry, however, requires expensive equipment and is typically difficult to access.

In working with her clients, Gaffen uses the Mifflin-St. Jeor equation, which according to one study, typically calculates BMR to within 10 percent of the measured value. The calculations for men and women are as follows:

Men: 10 × weight (kg) + 6.25 × height (cm) – 5 × age (y) + 5
Women: 10 × weight (kg) + 6.25 × height (cm) – 5 × age (y) – 161

Want to know how many calories you burn in a full 24 hours?

“There are online calculators that you can use to estimate the number of calories your body burns in a day,” Gaffen says. “These calculators take into account your current weight, sex, age, height, and physical activity level.” She recommends Body Weight Planner from National Institutes of Health and Get Your MyPlate Plan, a widget on the USDA’s MyPlate website.

Although these calculators exist, a dietitian would be your best and most accurate resource for determining your BMR.

Can You Influence How Many Calories You Burn Sleeping?

Many of the factors that determine your BMR and, therefore, how many calories you burn sleeping are beyond your control. It’s possible to elicit a minor boost by gaining muscle mass, as one pound of muscle burns more calories than one pound of fat. While muscle is more metabolically active than fat, research suggests that gaining muscle mass likely won’t significantly affect calorie burn.

In one study, previously sedentary women who participated in six weeks of resistance training experienced a significant increase in their BMR. Yet, despite the bump, none of the women lost weight or saw a remarkable change in their body composition.

If your goal is to burn more calories over the course of a day, your best bet is to focus on what you do when you’re awake.

Exercise regularly and strive to be more consistently physically active overall, even when you’re not technically working out. Run errands on foot, take the stairs, or swap a sit-down conference call for a walking meeting.

Does Eating Before Sleep Affect Calories Burned at Night?

Simply digesting food burns calories, so eating at any time — including bedtime — will cause a temporary boost in energy expenditure. But late-night meals probably won’t bolster (or, for that matter, sabotage) any weight-loss goals.

“It appears that what matters most in humans is how much you eat, as opposed to the time you eat,” Gaffen says. An apple contains the same amount of calories, whether you eat it for breakfast or a midnight snack.

However, the time of day can impact your behaviors around food. “It is common to mindlessly snack in the evenings when relaxing or watching TV,” Gaffen says. “This habit can lead to consuming more calories, which can lead to weight gain. So if you’re reaching for a snack in the evening, just try to stay mindful of snack choices and portion sizes.”