Counting on how many calories your fitness device says you burned today to justify dessert? Pass.
New research shows that seven devices designed to track calories burned are “way off the mark,” says Euan Ashley, DPhil, senior author of a paper published May 24 in the Journal of Personalized Medicine.
The worst-performing device was off by more than 50 percent; the best by an average of 27 percent.
But the news isn’t all bad.
Heart rate tracking “performed far better than we expected,” with an error rate on six devices of less than 5 percent, says Ashley, professor of cardiovascular medicine, of genetics and of biomedical data science at Stanford.
His team used medical equipment to monitor 60 volunteers who wore fitness trackers — an Apple Watch, Basis Peak, Fitbit Surge, Microsoft Band, Mio Alpha 2, PulseOn and a Samsung Gear S2 — as they ran or walked on treadmills, or pedaled stationary bikes.