A new report says fitness trackers are not so accurate  measuring the amount  calories our body burns while exercising, and that this may lead people to make poor decisions  their diet. The study is  Stanford University  the USA. Researchers evaluated the accuracy  five popular trackers. These included the Apple Watch, Microsoft Band, Fitbit Surge and Samsung Gear S2. The researchers observed 60 volunteers  they walked, ran and cycled while wearing the devices. Researchers found that none  the devices had an error rate  20 per cent. Dr Euan Ashley, co-author  the study, said: "People need to know that  energy expenditure, [the trackers] give rough estimates."
The Stanford scientists said users  fitness trackers should be cautious  using the devices to judge what they eat. Dr Ashley said: "If you go to the gym, and you think you've lost 400 calories, then you might feel you've got 400 calories to play ." This could be a problem  those who base what they eat  how many calories their fitness tracker said they burned. One CEO  a fitness tracker company suggested the researchers may not have adjusted the user settings properly. The CEO told the USA Today newspaper that the study method could have reported incorrect data, saying: "We think the excess error reported  energy expenditure is not representative  this study, due to this methodological error."