How Accurate Are Calorie Counters and Fitness Trackers? - Verily
You could be relying on a tracker that studies show to be off by 93 percent.

When it comes to healthy living, cool gadgets that advertise how they can help us make better fitness and nutrition choices sound awesome. But does wearing a fitness tracker actually make you healthier?

Well, it depends. Last month, Standford University researchers reported that of the fitness trackers they evaluated—Apple Watch, Basis Peak, Fitbit Surge, Microsoft Band, Mio Alpha 2, PulseOn, and the Samsung Gear S2—"none of the seven devices measured energy expenditure accurately." Even the most accurate device (the Fitbit Surge) "was off by an average of 27 percent. And the least accurate was off by 93 percent," the study notes.

Energy expenditure is the amount of energy (or calories) your body needs to carry out physical functions like breathing, blood circulation, digesting food and exercising, usually measured as calories burned. When these fitness trackers are off, though, it could spell trouble. "People are basing life decisions on the data provided by these devices," said Euan Ashley, DPhil, FRCP, professor of cardiovascular medicine, of genetics and of biomedical data science at Stanford. By allowing ourselves to eat a doughnut after a workout because we "burned it to earn it," we're oversimplifying complex processes in our body. Ashley said that making choices—like how much you eat or how effective your workout is—based on how many calories your device says you burned is a really bad idea.

If you're in the calorie-counting club and want to know how many calories you've burned to manage your weight, here's one major reason why a fitness tracker will be misleading: it doesn't know your fitness level. Even if a fitness tracker could tell the difference between a 150-pound sedentary woman and a 150-pound athletic one running at the same speed and pace, it can't account for the food she just ate or how much stress she's under. Wearable fitness trackers can get us into a bad habit of thinking that our body's fuel reserves start at 0 calories every day. It doesn't consider the fuel reserves that our body already has, maybe from Friday night drinks or eating a big Sunday brunch. Your height, weight, body composition, how much effort you're exerting, how healthy you eat and sleep—all of these are critical pieces of information needed to accurately measure energy expenditure. 

In fact, the Journal of the American Medical Association recently published research reporting that using a wearable device doesn't actually improve weight loss. Over its two-year study, young adults ages 18 to 35 who completed a prescribed diet and exercise plan lost more weight without using a fitness tracker than those who were in the wearable device group—13 pounds versus 7 pounds, respectively. 

Fitness trackers aren't doctors or medical devices that can give us a full picture of how the human body works. If wearing one encourages you to take more steps every day, exercise more, eat healthier, and sleep better—that's great! But don't let it mislead or distract you from making the best decisions for your health. 

Sleep well. Put the hard work into your workouts. Eat real food. Keep your stress levels to a minimum. At the end of the day, the only tracker you can truly count on is listening to what your body is telling you, whether and how it responds to the choices you make in honor of your health.

Photo Credit: Filip Mroz