Researchers at Stanford University have released a study concluding that wearable fitness trackers provide inaccurate measurements when it comes to providing information to users on how many calories have been burned.

The researchers evaluated seven wearable fitness trackers and how they measured heart rate and calories burned. Most of them measured heart rate pretty accurately, but all seven had error rates of 20 percent or higher in measuring the calories burned by the user.

Although most of us would find an 80 percent accuracy rate to be in the ballpark for general knowledge on how many calories we burn in a day, the researchers concluded that the error rate of 20 percent or more emphasized the limitations around wearable devices and their accuracy to measure and report vital signs in the clinical setting.

The inaccuracies make it difficult for physicians to rely on the data in a clinical setting so the researchers challenged the device manufacturers to share validation data so health care providers can rely on the information and integrate them into the care and treatment of patients.