Study: Don't trust fitness trackers for calories burned

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Study: Don't trust fitness trackers for calories burned. Ali Gorman reports during Action News at 5 p.m. on May 25, 2017. (WPVI)

If you're using a fitness tracker to count how many calories you burn, researchers at Stanford University School of Medicine caution the number could be way off.

And it could sabotage your diet.

They tested several of the top wristband activity monitors, and found that none measured energy expenditure well.

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

The least accurate was off by 93-percent.

The most accurate, the Fitbit Surge, was off by about 27-percent.

Most likely, it over-calculated the number of calories burned.

That could lead you to eat extra calories, and then wonder why the weight isn't coming off.

Unlike other studies, this one showed that the monitors measured heart rates well.

6 of the 7 were within 5 per cent of what was recorded by medical-grade monitors.

"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.

For more on Stanford's study, click here.

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