To be alive is to consume energy. Movement requires calories, but so does pumping blood, taking breaths, and performing other essential functions. When you read or watch TV, your body hums along in the background, churning through about 100 calories an hour. But what if you want to speed up your metabolic rate, break a sweat, and have your body devour lots of calories? Then you have to ramp up the activity levels.
As a rule of thumb—or a rule of the body—cardiovascular and aerobic exercises burn the most calories. “Generally, anything that’s going to increase our heart rate higher is going to burn more calories,” says Steve Herrmann, a research assistant professor who directs the University of Kansas Weight Management Program and maintains the Compendium of Physical Activities, a health reference guide that compiles energy costs for different exercises and activities.
Targeting the biggest calorie burners on the list won’t be the right fitness approach for everyone. If you’re still getting in shape, it’s most important to “start the habit of being active,” Herrmann says. Walking several times a week will give you a strong foundation to build on. You can then layer in strength training, and ultimately, find a workout routine you enjoy doing regularly that maintains your fitness levels. “If high-intensity interval training gets you there, that might not be the thing that sustains you,” Herrmann points out. Some people realize they’re fond of solo jogs or bike rides. Others stay motivated by exercising alongside friends.
Behind the calorie burn
In concept, calories are nothing more than a measure of energy. The calorie was first defined as the energy required to heat a gram of water by 1°C—scientists later officially tied it to the joule, another energy unit. Nutritional calories, or kilocalories, are 1,000 times that. There are four nutritional calories per gram of carbohydrate or protein, and nine calories per gram of fat.
In reality, and especially within the biological machinery of your guts, simple caloric math falls apart. While every nutritional label includes a standard measure of calories, your actual caloric intake depends on multiple factors tied to your body. The microbes in your intestines are one example. As a result, some people might use up more calories as they digest food; some store more calories as fat; and some excrete more calories when nature calls.
The rate at which you burn calories, too, can be influenced by many factors, including age, genetics, and muscle tone. In general, the more you weigh, the more energy you expend doing a given activity because you have to move more mass, Herrmann explains. As people lose weight, they have to increase the duration or intensity of an exercise to burn the same amount of calories.
Should you count calories?
Thinking about calories can be useful in both planning out meals and workouts. “As a whole, the ‘calories in, calories out’ philosophy is a good one,” says April Ho, a dietitian and personal trainer at the University of Rochester Medical Center. “Your body has to burn more calories than you’re taking in if you want to lose weight.” But it also has its limits: Ho cautions that relying on calorie-counting tools might give an unearned sense of precision, thanks to the sheer amount of variables that influence how many calories you absorb and use up. Don’t strain yourself trying to “estimate the exact numbers,” she says, “because you’re probably going to be wrong anyways.”
It can even be difficult and expensive to measure calories in experiments. One method is to have people drink doubly labeled water, which carries harmless radioactive versions of hydrogen and oxygen through a subject’s body. Observing the tagged elements in urine or other fluids lets scientists calculate an exerciser’s energy expenditure throughout a day.
But the most accurate way to assess someone’s metabolic rate is with a direct calorimeter. This small, sensor-filled room monitors heat produced by people as they move around inside. The tool isn’t for everyday use—it takes about $1 million to build one of the rooms, which is why Herrmann knows of fewer than a dozen in the US.
Exercises that burn the most calories
Below are the most calorie-burning exercises, based on the University of Rochester’s calorie burn rate calculator. All values are based on one hour of activity and the average weight of Americans ages 20 or older, which according to the Centers for Disease Control and Prevention, is 170 pounds for women and 200 pounds for men.
Running at 6 mph: 1,400 to 1,600 calories
Thanks to bipedalism, humans are capable long-distance runners, often using the most energy-efficient speeds to keep pace over many miles. (Some scientists hypothesize that our species evolved to be good runners to pursue prey over long stretches.) Jogging at slower speeds uses fewer calories per hour: The more ground you cover, the more energy you consume. Treadmills burn fewer calories, generally speaking, than running outdoors.
Cycling at 20 mph: 1,400 to 1,600 calories
Biking, like running, is another exercise that gets the heart pumping and engages many muscle groups. Stationary biking uses up less energy than pedaling on the road—about 900 to 1,000 calories per hour at max speeds. “When you’re inside on a stationary bike, your shoulders are relaxed, you don’t have to turn,” Herrmann points out. There’s also no wind to contend with. To increase the burn on a machine, you can crank up the resistance or add small dumbbells.
High-impact aerobics: 800 to 960 calories
Ho recommends two types of workouts to increase a metabolic rate and keep it elevated after an exercise is over. One, circuit training, involves “strength training and cardio at the same time,” she says, like swiftly moving from squats into crunches without breaks between each activity. The other, high-intensity interval training, can similarly “increase your metabolic rate for several hours longer than other types of exercise,” Ho says. This is cardio with bursts of high output, such as a minute of sprints followed by three minutes of more moderate activities.
Swimming laps: 800 to 1,000 calories
Moving through water works out limbs and elevates heart rates while avoiding the joint stress of footfalls on pavement. But what about a long dunk in a chilly pond? A scientific review published in 2022 found that swimming in ice water may reduce the risk of diabetes and other disorders. As for other touted benefits, such as weight loss, the evidence wasn’t clear, the authors determined.
Weightlifting: 500 to 580 calories
As you might suspect, the heavier the weights you lift, the more calories you will burn. Building muscle tone can also make everyday tasks and common motions a little easier on your body. But it’s important to remember that you have to build up to bigger dumbbells, barbells, and kettlebells—going from 0 to 100 raises the risk of tears and other injuries.
Sports: up to 960 calories
There’s a maxim among some fitness gurus that “the best workout is the one you’ll do.” Though it’s cheesy, there’s truth to it. If you enjoy participating in sports—and this taps into the community spirit of exercise that Herrmann encourages—know you’re burning calories as you play. An hour of martial arts such as karate and kickboxing eats up 840 to 960 calories. Water polo? 800 to 960. A game of basketball? 670 to 770 calories. Even certain video games can consume more calories (think enthusiastically ducking and swinging your arms in Wii Tennis or VR games such as Beat Saber), which convinced Herrmann to include gaming in an upcoming revision of the Compendium of Physical Activities.