Constantly checking the calories burned on your fitness tracker to determine what to eat? Then tuck it away and read on, because you might not want to indulge in that second piece of cake. NPR reports that cardiologist and professor Euan Ashley responded to his tech-savvy patients’ frequent requests to analyze their wristband data by conducting a study to test the wristbands' accuracy. He took a look at seven of the most popular fitness tracker models with his colleagues at Stanford and compared two metrics, heart rate and calorie burning statistics, with the medical tests doctors utilize. While the heart rate data measured up well to EKG tests (with most devices being only about 5% off), calorie trackers were nowhere near accurate.
Compared to indirect calorimetry, a highly sophisticated method of tracking metabolism used in doctor’s offices, wristband tracking outputs for calories burned were anywhere from more than 20% to 93% inaccurate. And professor of preventative medicine Dr. Tim Church believes relying on this wristband data can do more harm than good: "It's just human nature. People are checking these inaccurate counts and they think they've earned a muffin or earned some ice cream and they're sabotaging their weight-loss program." The Guardian reports that the device with the most inaccurate calorie tracker was PulseOn (getting it wrong 93% of the time), while FitBit Surge performed the best, but was still off by 27%. PulseOn issued a statement questioning the accuracy of the study, saying researchers "may not have properly set all the user parameters on the device." (Read more fitness stories.)