Over the course of a day, your body’s natural calorie burn without any activity can range from 1,300 to more than 2,000, depending on your age and sex. (More on that in a bit.)
So, how and why do you burn calories reading, sleeping or logging long hours as a couch potato? Let’s do the math with endocrinologist and weight management specialist Marcio Griebeler, MD.
Why your body burns calories
With so much talk about “calorie burn” focused on weight loss, the true reason behind your body’s calorie needs often gets overlooked. It’s not about the numbers on the scale. It’s about survival.
“To live, you have to burn calories,” says Dr. Griebeler. “Your body burns calories to pump your heart, to breath, to think … to do everything.”
That constant burn to keep your body going is known as your metabolism. To get a little more specific, your basal metabolic rate (BMR) refers to the minimum number of calories your body needs to function.
So, as you’re doing nothing, your body is still busy and burning calories to keep all systems operational.
Calculating your metabolic rate
While we all have a BMR, we don’t all share the same BMR. It’s not some standard formula like the Pythagorean Theorem. (That’s A² + B² = C², in case you’re rusty on your middle school math lessons.)
BMR, also known as your resting metabolic rate, varies widely based on factors such as:
- Age.
- Height.
- Weight.
- Sex.
- Muscle-to-fat ratio.
- Genetics.
Doctors Without Waiting Rooms 