meIf you use a fitness tracker, or even just an exercise machine at home or at the gym, what’s the most notable metric it shows? In most cases, it’s probably an estimate of how many calories you’ve burned. In fact, on most devices, you can’t turn off calorie counting even if you want to.
However, these estimates are notoriously inaccurate: A Stanford University School of Medicine study compared seven different fitness trackers worn on the wrist and found that the the majority the precise estimate of energy expenditure (in other words, calories burned) was off by 27 percent. The least accurate was a whopping 93 percent off. Neither device provided estimates of energy expenditure “within an acceptable range of error,” the researchers concluded.
This won’t surprise anyone who knows the truth about calorie counting. Food labels that tell you how many calories are in packaged foods? Those are also highly unreliable, because they’re based on averages that don’t really take into account how our bodies digest different foods. They’re closer than calorie-burn estimates, though: The Food and Drug Administration only allows inaccuracies of up to 20 percent.
So if these numbers are essentially meaningless, how did we come to accept them as standard? And why do they have such staying power over seemingly every new piece of tuning tech released?
How calorie counting took over our brains
The history of counting calories dates back to the 19th century and is quite strange. The calorie has been around as a measure of energy since the 1820s, but it wasn’t originally used to measure anything in the human body. That is, until 1896, when a researcher named Wilbur O. Atwater placed a graduate student inside a calorimeter, a device designed to measure the energy generated by explosives and engines. The machine measured everything the student ate and his energy output, showing that human bodies absorb and emit energy like machines, or pumps (ouch!).
However, counting calories for weight loss didn’t become popular until a couple of decades later. That happened in 1918, when the doctor and columnist Lulu Hunt Peters published a book called Food and Health: with Key to Calories.
It goes without saying that our understanding of the human body has come a long way since 1918. We know, for example, that the nutritional value of food goes far beyond simply estimating the number of calories you consume. maybe absorb from it. And the many health benefits of exercise are not reflected in a single number.
“People need to understand that these calorie counters are based on algorithms and your body is not an algorithm. Your body needs specific things that other bodies don’t,” says Kerry O’Grady, national wellness liaison for the National Eating Disorders Association. Different bodies absorb and burn calories differently (and obviously need more than just calories). “The more we buy these numbers, the more we stop listening to our own bodies.”
“Calorie counters are based on algorithms, and your body is not an algorithm.” —Kerry O’Grady
For her, it’s personal. “I lived through this,” she says. “I almost died of anorexia when I was in my early 20s. I can’t use a tracker because it’s too stimulating for me.”
That is not unusual. Experts generally suggest that anyone with a history of eating disorders, orthorexia, or obsessive habits around exercise and nutrition stay away from fitness trackers. Even those without that history may find that trackers make healthy habits less satisfying. “Quantifying everything takes a lot of joy out of movement and food,” says personal trainer Lauren Pak. “It makes working out and eating feel clinical, like a job.”
Some of us can look at calorie counts and ignore them, but many people are affected more than they realize. “I think the hardest part of breaking away from calorie counting is that a lot of us who have some experience with it could stop tracking, but calorie data lives for free in our brains,” says Jessi Haggerty, RDN , a certified intuitive eating counselor and personal trainer. For example, if you feel like you’re not allowed to “indulge” in certain foods on days you haven’t exercised, you may not have done the exact math, but you’re still thinking about nutrition and exercise in a way that’s formed by counting calories.
And that idea you have of how many calories you need in a day? It’s probably wrong, says Rena Eleázar, DPT, physical therapist, athletic performance coach, and competitive weightlifter. “Almost across the board, the athletes I work with have this illusion of how many calories they’re expending, and usually they don’t eat enough,” she says.
A double edged sword
Wearables and connected devices can help some people stay consistent with an exercise routine and remind them of their goals. And some of the data trackers collect can be useful. For example, heart rate information can help highlight exercise intensity and monitor safety for some people with chronic health conditions. Other measurements, like heart rate variability, can give you useful information about how well you’re handling stress, both physical and mental.
But the ubiquity of calorie counting in fitness trackers makes diet culture hard to escape. “What’s helpful and what’s not is very person-dependent,” says Pak. “You should be able to choose what you want to track. People shouldn’t be assumed to have a weight loss goal associated with physical exertion.” With some systems, you can basically play your way out of calorie counting by not entering your weight; others will still display an (even more bogus) number. of calories by automatically substituting an “average” weight.
Counting calories just isn’t a good way to know what your body needs and can cause you to restrict what you’re eating in a way that quickly becomes unhealthy, says Haggerty. The only situation where calorie tracking might be useful, he says, is for people who struggle to eat enough to keep up with their training, a common problem among endurance athletes. “Still, there are ways to do it that don’t require follow-up,” she says. If you’re having trouble determining what or how much you need to eat, Haggerty suggests working with an anti-diet or Health at Every Size-aligned dietitian. Good rules of thumb for people who are training hard, she says, are to aim for three meals and three snacks per day, and eat within the first hour of working out.
So why do digital devices still include calories?
Most of the digital fitness companies contacted for this story declined to comment on the record, though some confirmed they do see consumer demand for calorie-burn estimates. “They’re ubiquitous because people want them,” says O’Grady. “If the market didn’t demand them, they wouldn’t be there. Although many people know those numbers are inaccurate, they would be upset if they were removed. That’s what these tech companies rely on. They want you to have a relationship with that number.”
Diet culture is so deeply ingrained in many of us that we can’t mentally unlink calories and exercise, even when we know better.
So does that mean you should end your fitness tracker? If you find yourself paying more attention to the numbers on the screen than how your body feels, maybe. “You can pretty well gauge how well your nutrition is going based on how you feel in the gym,” says Eleázar. If you’re exhausted during every workout, that’s a sign that something needs to change and you most likely need to eat more. Trust that sense of your own body over any tracker.
And even if you’re determined to track your workouts, don’t underestimate the benefits of going analog. You can always use an old-school pedometer to count your steps, or grab a stopwatch to time your intervals, for example. “I think just writing down the details of your training is great,” says Pak. “Then you can track the progress you made from week to week. Maybe this week you did three sets of 10 squats with 25 pounds, and next week you do three sets of 10 with 30 pounds. That is great progress.”
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