The Question: Just how accurate is the "calories burned" display on my treadmill? Should I keep track of how much I'm burning off if I'm trying to lose weight?
Answer: That number is just an estimate, and it's unclear whether knowing it will help you lose weight.
Exercise trackers and fitness equipment typically estimate the number of calories you burn when you exercise, but experts say you shouldn’t put too much stock into that number -- and shouldn't rely on it to help you lose weight.
Paying attention to calories burned during exercise could also feed into an inaccurate and counterproductive transactional mindset that leads to mindless overeating and weight gain in the long run, says E. Todd Schroeder, director of the Clinical Exercise Research Center at the University of Southern California.
There are several problems with focusing on the number of calories linked to a certain exercise. For one, people tend to overestimate the calories they’ve burned while exercising and underestimate the calories they consume, which could lead to a miscalculation that prevents them from achieving their weight goals.
Secondly, people tend to feel like they’re “entitled” to eat more after a workout, which could lead to weight gain in general.
“If they think they burned more calories than they did, then they say, ‘I can enjoy a Frappuccino because I did a hard workout,’” Schroeder said. “That’s a big issue.”
And finally, thinking of exercise in such a goal-oriented way may take away from the pleasure of doing the physical activity, which over time could increase the likelihood of dropping out.
How your body adjusts to more physical activity over time
There’s even some evidence that your body limits the number of calories it burns in a single day. Research shows that over time, bodies adapt to higher activity levels and eventually become more efficient about the calories they use, says Herman Pontzer, an evolutionary biologist at Hunter College.
Pontzer’s recent study comparing calorie expenditures across many different cultures showed that hunter-gatherers in Tanzania burned about the same amount of calories as an office worker in the U.S. This could be for at least two reasons, he explained. The first theory is that, over time, your body accommodates your level of physical activity by expending fewer calories to execute basic functions, like keeping your immune system running.
“If you increase your activity level a bit, what we see is that your total energy expenditure doesn’t change,” says Pontzer. "But that’s not because you got more efficient at running or walking -- your body probably carved a little bit of energy out of all those other tasks to make room for those increased running or walking costs."
The second theory is that active people might compensate for their exercise in subtle, subconscious ways, like resting more after the activity or remaining sedentary for the rest of the day after a workout.
What calorie counting can do for you
Despite these limitations, most experts agreed that calorie counts might be helpful to get a rough baseline for your activity, as long as you understand that it’s an estimate and probably doesn’t reflect the precise number of calories your body is actually using, says Dr. Pamela Peeke, a spokesperson for the American College of Sports Medicine and author of the book Body For Life For Women.
Schroeder concedes that counting calories burned can be useful for people who want to judge their workouts against past performances and use the same machine to calculate it every time.
But instead of setting a calorie goal with exercise, it’s more valuable to feel present in your body as you move, because it allows you to concentrate on form and intensity, Peeke explained. Her advice: Once or twice, look at the calories display to get a ballpark estimate of what you’re working with, but mostly you should focus instead on how your body feels during the physical activity.
"You can’t pay attention to your body and your numbers,” Peeke said. "Feel it through.”
How to get an accurate calorie count
Most exercise machines and calorie tracking apps and devices estimate the calories you burn based on data you enter about your age, sex and weight, but things like body composition, training level and exercise intensity all play a role in how many calories you truly burn. And this true number can only be calculated in a lab that measures either the amount of heat your body is giving off, or the amount of oxygen you take in as you exercise.
But if you'd like to see a estimate, if only to underscore just how difficult it is to "burn off" part of what you eat every day, here's a chart of common activities and the approximate number of calories that a 125-, 155- and 185-pound person would burn after 30 minutes.
Reminder: Exercise is less efficient than diet for weight loss
There are so many benefits to physical activity, including increased stamina, stronger muscles and disease prevention, but creating a calorie deficit for weight loss is the least of them. So much hard work can be “undone” in a single high-calorie snack or drink, which is why nutritionists and obesity experts tell people to focus on diet when trying to lose weight.
"Nutrition is what’s going to get you there,” Peeke concluded. "What the physical activity does is optimize what you did in the kitchen."
“Ask Healthy Living” is for informational purposes only and is not a substitute for medical advice. Please consult a qualified health care professional for personalized medical advice.