Fitness trackers and smartwatches were among the hottest prospects of this holiday season. These wrist-worn devices boast a number of features to monitor your day-to-day activities and keep track of your health. However, if you have got one such fitness tracking device this festive season and are thinking of using it during your workout session, then there’s some bad news for you. A study by Stanford University revealed that fitness trackers, like the Apple Watch and Fitbit, are largely inaccurate in measuring the calories burnt.
Stanford researchers conducted tests on the Apple Watch, Basis Peak, Fitbit Surge, Microsoft Band, Mio Alpha 2, Pulse On, and Samsung Gear S2. 60 volunteers were continuously monitored and assessed while sitting, walking, running, cycling and working out on treadmills. They compared the data produced by the devices to a medical grade electrocardiograph. The study found that none of the devices could give the correct number of calories burned.
The devices reported the lowest error for cycling and the highest for walking. Most of the devices reported an error of below 5% for heart rate while cycling. But none of the devices could achieve an error below 20% of calories burned.

The researchers from the university concluded that the devices were quite accurate at measuring the heart rate of the user. But when it comes to measuring the calories burnt, the devices were off by a huge margin.
“The heart rate measurements performed far better than we expected,” said Euan Ashley, lead author of the university release. “But the energy expenditure measures were way off the mark. The magnitude of just how bad they were surprised me. People are basing life decisions on the data provided by these devices.”
As the experiment was conducted on selected devices, there’s no way to tell if all the fitness trackers in the market are as bad as these seven. Some of the newest devices in the market like Samsung Gear Fit2 Pro and Gear Sport might do better, but who knows! Since these are experimentally obtained results, caution is suggested in the use of fitness trackers for measuring calories burnt.