Last month, researchers at Aberystwyth University examined three popular fitness trackers — the Fitbit Charge 2, the Letscom HR and the Letsfit — and exposed that they significantly miscalculate the number of calories we burn while exercising. And just so everybody knows, this discovery obviously explains why I have a beer belly even though my Fitbit says I lost exactly 100,000,000,000,000 calories since the New Year.
To come to these findings, the researchers asked six men and six women to walk and jog on a treadmill while measuring the oxygen they burned — using high-tech equipment, the scientists were able to accurately calculate the number of calories each participant burned based on the amount of oxygen they consumed. “There is a direct relationship between the amount of energy somebody is using and the amount of oxygen they are burning,” lead researcher Rhys Thatcher explained in a press release. “If you know how much oxygen you’ve burned, we can then know accurately how many calories you’ve expended throughout the activity.”
Using this technique, the researchers found that the Fitbit Charge 2 underestimated the number of calories burned while running by four percent, but it also overestimated the number of calories burned while walking by more than 50 percent. Meanwhile, the Letscom HR underestimated the number of calories burned while running by 33 percent, and it overestimated the number of calories burned while walking by 15.7 percent. Finally, the Letsfit underestimated the number of calories burned while running by 40 percent and overestimated the number of calories burned while walking by two percent.
All of which means calories are a goddamn mystery, and unless you’ve got a team of scientists at your disposal, nobody really knows how many they burn on a regular basis. But according to Thatcher, in the same press release, that simply means we should all take a more relaxed approach to calorie counting anyway:
“Activity trackers definitely have a role to play in improving health. We all like to see ourselves progress; you have to interpret the data coming out of them with care — they are not direct measurements. However, they can be useful to compare what you’re doing today with what you did yesterday, what you’re doing this week compared to last week, so you can see progression and that can be a great motivational tool to help people to stick to an exercise programme.”
Furthermore, Thatcher encourages everyone to do more exercise no matter what their fitness tracker says:
“Activity is one of the biggest determinants of health. Increasing the levels of activity is important; a 5-minute walk is better than nothing, and a 10-minute walk is better than a 5-minute walk. There are benefits to be gained from increasing activity across the board.”
Now, the fact that calorie counters are less than accurate isn’t exactly news. While researchers, like those who conducted this research, generally rely on highly specialized monitors — like the metabolic cart, which measures oxygen used — real-world calorie counters depend on more general statistics, like your weight and age, to predict how many calories you burn.
The Fitbit website (kinda) explains how their device calculates the number of calories burned: Basically, it analyzes your data — your age, gender, height, weight — and uses these statistics to estimate your basal metabolic rate (how quickly your body burns calories while resting). From there, the device uses an accelerometer and some manually entered activity in an attempt to calculate how many calories you burn while exercising. As you might imagine, this is better than throwing a dart at a number while blindfolded, but accurate it is not.
This estimative approach is similar to how exercise machines, like treadmills, calculate calories burned. They essentially guess your heart rate based on your pace. However, they can’t — as an example — account for the fact that you’re hanging onto the handlebars for dear life, which means they may very well overestimate how many calories you actually burned.
“People are too complex for those counters and whatnot — it’s too general,” says Jeff Jalaba, a certified personal trainer in L.A. “It really is throwing out this kinda ambiguous number. For everybody, what matters way more is what those calories are made up of.”
Certified personal trainer Landon Brown reinforces this idea. “It’s a ballpark guess within a ballpark guess,” he says, before diving into a more reliable fitness method than straight-up calorie counting. “Remember your basal metabolic rate [which you can calculate here], stick to a nutrition plan that fits your goals and put forth the effort that matches those goals.”
If that sounds too complex, Jalaba emphasizes that exercising more and eating better — without feeling the need to count calories that might not even be worth counting — might be a more reasonable approach to a healthier lifestyle.
“It sucks that we can’t have that instant gratification that comes with seeing how much caloric ass we kick in reality,” Brown says. “That doesn’t, however, mean we can’t be just a tad bit ignorant and enjoy the technology.” In other words, much like Thatcher said in the press release, counting calories sometimes turns a less than precise adventure — i.e., getting healthy — into one that’s too meticulous for our own good. But then again, if watching those calories add up provides motivation, that might not be the worst thing, even if that number is just an estimate.
Essentially then, if you want to lose weight — and stop me if you’ve heard this one before — your best bet is to exercise more and eat better, no matter what your calorie counter says. There really is no getting away from it, is there?