Feeling the “burn” from your fitness band or watch? There was (and still is) a lot of hype around high-tech fitness watches that in some instances cost several hundred dollars. Are any of them worth it, and what’s up with those subpar reviews? It turns out that they might not be as effective or on track as marketers promised, and that has some fitness buffs steaming.

For example, a new study from Stanford University published in the Journal of Personalized Medicine found that fitness trackers, while accurate at monitoring heart rates, aren't very accurate when it comes to counting calories burned. Researchers tested seven wristband fitness monitors: the Apple Watch, Basis Peak, Fitbit Surge, Microsoft Band, Mio Alpha 2, PulseOn and the Samsung Gear S2. None of the devices measured energy expenditure correctly, according to the study. The most accurate device (FitBit Surge, according to The Guardian) was off by 27 percent, and the least accurate one (PulseOn) was off by 93 percent.

“People are basing life decisions on the data provided by these devices,” said Euan Ashley, a professor of cardiovascular medicine, genetics and biomedical data science at Stanford, in a news release. "But consumer devices aren’t held to the same standards as medical-grade devices, and it’s hard for doctors to know what to make of heart-rate data and other data from a patient’s wearable device," according to the release.

Et tu, step counts?

Fitbit dataA person wearing the FitBit Force holds a smartphone displaying data collected by the recently recalled fitness tracker. (Photo: Justin Sullivan/Getty Images)

Calorie counts aren't the only metric that may be untrustworthy. In 2015, Nike FuelBands took some heat after a study found it miscounted steps by about 27 percent. For the test, researchers undertook the exact same workouts wearing two different Nike FuelBands. They ran the same miles, tackled the same hills, cycled the same loops and did everything the exact same way. However, one FuelBand promised a researcher he’d logged thousands more steps than the other.

The FuelBand certainly isn’t an anomaly. Podiatrist, fitness and tech writer Jim McDannald says that several of these devices are more marketing hype than reality. “People are getting fitness tracker fatigue; in large part, it’s because many of these devices are simply inaccurate,” he told the New York Times. “You may have burned more, or fewer, calories than they say. Or in my case, walked more steps.”

If you think it’s just hardware that has problems, think again. In another field test, the Moves and Breeze apps were tested on the same iPhone. Moves recorded 3,070 steps and Breeze reported 3,363. It was the exact same walk, the same phone, but a huge discrepancy. Even worse, on another day Breeze reported a goal of 3,500 steps had been taken even though the tester hadn’t taken a single step (he was sitting in a cube farm all day).

A better, more affordable solution

What’s a fitness fanatic to do? “Even a cheap pedometer is more accurate than these wristband trackers,” says McDannald, although he does note that such devices can encourage couch potatoes to get moving. Along similar lines, sleep trackers don’t have a much better reputation. Options like Jawbone Up, which is supposed to track sleep movements, have been called "easy to trick." However, this hasn’t stopped shoppers from buying.

The market research firm Gartner, Inc., estimated that 274.6 million wearable electronic devices were sold worldwide in 2016, an increase of 18 percent over 2015. "From 2015 through 2017, smartwatch adoption will have 48 percent growth largely due to Apple popularizing wearables as a lifestyle trend. Smartwatches have the greatest revenue potential among all wearables through 2019, reaching $17.5 billion," said Angela McIntyre, research director at Gartner.

Editor's note: This story has been updated since it was originally published in May 2014.

What you need to know about fitness trackers
Despite their continued popularity, fitness trackers may not deliver on the promises they make.