A report says fitness trackers don't measure the calories we burn while exercising so accurately. This means people may be making poor decisions about their diet. Researchers looked at five popular trackers, including the Apple Watch. The researchers observed 60 volunteers as they walked, ran and cycled. None of the devices had an error rate below 20 per cent. A researcher said the trackers only gave "rough estimates" for calories burned.
The scientists said people should be careful about using the devices to decide what to eat. A researcher 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." A CEO of a fitness tracker company said the study method could have used incorrect settings, which would give incorrect data. He said the study's error rate was wrong because of an error in the research method.