The word “calorie” may bring up thoughts of nutrition labels and treadmill readouts, but really calories are just units of energy. Your car runs on gas, your house runs on electricity, and your body runs on food energy. So how many calories do we burn each day, and how many should you burn? Let’s dig in.
You actually burn most of your calories at rest
Calories aren’t only burned during exercise. It takes energy to keep the lights on, so to speak—for your heart to beat, your brain to think, your cells to repair themselves, and more.
In fact, most of our calories are burned doing these maintenance chores. Scientists call this baseline calorie burn our "basal metabolic rate," or BMR. There are several equations that will estimate your BMR; for a calculator, try the one at tdeecalculator.net. (It uses the Mifflin-St. Jeor formula if you don’t know your body fat percentage, and the Katch-McArdle formula if you do.)
To give you an example, I plugged in my stats—I’m 150 pounds and 5’6”—and the equation guesses that someone my size burns:
1,352 calories for most of my basic bodily functions (not including digestion!)
1,623 calories, total, if I’m sedentary
2,096 calories, total, if I do moderate exercise three to five times a week
2,569 calories, total, if I’m a hardcore athlete or a person who exercises on top of having a physical job
Keep in mind these are just estimates; your actual calorie burn may be more or less. The factors that affect your total calorie burn include:
Body size: The bigger you are, the more calories you burn at baseline and the more you burn during exercise.
Muscle mass: Muscle burns more calories than other tissues (which is why you get a more accurate estimate if you know your body fat percentage; the lower your body fat, the more muscle you have by comparison)
Age: These formulas assume that your metabolism slows down a bit as you age (although there is evidence that this may not make a big difference)
Activity: The more you exercise, the more calories you burn
Genetics and other factors not accounted for in the formula: There’s actually a huge variety from person to person, even if you compare people of the same size, age, etc.
To give you a sense of the range, the Dietary Guidelines for Americans figures that a 5’10” man who weighs 154 pounds will burn, in total, between 2,000 and 3,000 calories each day, depending on his age and activity level. Their example woman is 5’4” and 126 pounds, and she will burn between 1,600 and 2,400 calories.
So if you’re used to thinking of 2,000 calories as some kind of upper limit for how much to eat—or 1,200 calories as a calorie budget for dieting—you may be surprised to realize how many calories you probably already burn.
How (and why) to burn more calories
If you’re trying to lose weight, logic would say that you should focus more on diet than exercise. After all, if most of your calorie burn is your BMR, exercise is going to be a drop in the bucket by comparison.
I don’t think that’s the only thing you should consider, though. If your BMR is 1,300 calories and your total burn is 1,600, then sure, you could eat 1,300 calories without exercising and probably lose weight. But it’s hard to be healthy while you’re eating so little.
Burning more calories through exercise helps your body in two ways:
Exercise is good for us, regardless of calorie burn; we should all be getting at least 150 minutes of cardio per week, plus some strength training to help build or retain muscle.
The more food you eat, the easier it is to fit in the good stuff: vitamins, minerals, fiber, good fats, and a variety of vegetables.
A person who burns 2,300 calories and eats 2,000 is in a much better position to benefit from exercise and good nutrition than a person who burns 1,600 and eats 1,300.
So how do you burn more calories? You can’t get younger, and if you’re losing weight you won’t want to get bigger. The biggest levers you can pull are:
Exercise more
Gain muscle mass (through strength training, and eating plenty of protein)
Don’t diet all the time
I’ve written before about how I’ve noticed my total calorie burn increases when I’m eating more food; when you feed your body, it’s more willing to expend energy. This is one of the reasons it’s thought to be beneficial to take “diet breaks” if you plan to be in a weight-loss phase for a long time.
Why you shouldn’t rely on “calorie burn” numbers from wearables or exercise machines
You’re probably wondering how much exercise is “enough” to burn more calories. It’s a trick question, though: You want to change what kind of person you are—stop being sedentary and become a frequent exerciser—rather than nickel-and-dime yourself about exactly what numbers you burned in which workout.
This is because our bodies get more efficient with exercise over time. A half-hour jog might burn 300 calories in theory, but at the end of the day you may have only burned, say, 200 more than if you hadn’t jogged. You might end up feeling more tired later in the day, or you might just be getting better at running and burning fewer calories when you do it. (This is an ongoing area of scientific research.)
There is evidence that exercise machines’ estimates of calorie burn are extremely inaccurate; wearables like Fitbits and Apple Watches are probably a bit better, being personalized to your exercise intensity, but they’re still ultimately relying on estimates that aren’t always accurate.