A new says fitness trackers don't measure the our body burns while exercising so . This means people may make decisions about their . The study, from Stanford University, evaluated five popular trackers. These included the Apple Watch, Fitbit Surge and Samsung Gear S2. The researchers observed 60 as they walked, ran and cycled with the . Researchers found that of the devices had an error below 20 per cent. Dr Euan Ashley said: "People need to know that on energy expenditure, [the trackers] give estimates."
The scientists said of fitness trackers should be about using the devices to judge what they eat. Dr Ashley said: "If you go to the , and you think you've lost 400 , then you might feel you've got 400 calories to play with." This could be a for people who decide what to eat after reading fitness tracker . A CEO of a fitness tracker company told the USA Today that the study method could have used incorrect and thus given incorrect data. He said the study's error rate was wrong of a "methodological error" in the .