A new report says fitness trackers are not so accurate in measuring the amount of calories our body burns while exercising, and that this may lead people to make poor decisions about their diet. The study is from Stanford University in the USA. Researchers evaluated the accuracy of five popular trackers. These included the Apple Watch, Microsoft Band, Fitbit Surge and Samsung Gear S2. The researchers observed 60 volunteers as they walked, ran and cycled while wearing the devices. Researchers found that none of the devices had an error rate below 20 per cent. Dr Euan Ashley, co-author of the study, said: "People need to know that on energy expenditure, [the trackers] give rough estimates."
The Stanford scientists said users of fitness trackers should be cautious about 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 with." This could be a problem for those who base what they eat on how many calories their fitness tracker said they burned. One CEO of 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 in energy expenditure is not representative in this study, due to this methodological error."