Your fitness tracker could be incorrect

27 July 2017

Most fitness trackers do a poor job of measuring calories burned, researchers claim.

Academics at Stanford University School of Medicine have studied seven wristband activity monitors, as worn by a diverse group of 60 volunteers.

The devices evaluated were the Apple Watch, Basis Peak, Fitbit Surge, Microsoft Band, Mio Alpha 2, PulseOn and the Samsung Gear S2.

In all, the researchers found that the devices "adequately" measured heart rate, but gave "poor estimates" when it came to measuring energy expenditure or calories burned.

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Even the most accurate device was off by an average of 27 per cent and the least accurate was off by 93 per cent.

"The heart rate measurements performed far better than we expected," said Professor Euan Ashley. "But the energy expenditure measures were way off the mark. The magnitude of just how bad they were surprised me."

For the study, volunteers wore the wrist devices while walking or running on treadmills or using stationary bicycles. Each volunteer's heart was measured with a medical-grade electrocardiograph, while the metabolic rate was estimated with an instrument for measuring the oxygen and carbon dioxide in breath. The two results garnered from the wearable devices were then compared to measurements from the two "gold standard" instruments.

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In conclusion, Professor Ashley stated that fitness tracker users shouldn't base their diet on the number of calories a device claims you have burned. His team is now conducting a study to test the accuracy of devices in the real world.

The full study has been published in the Journal of Personalized Medicine.

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