Fitbits Overestimate Calories Burned While Walking By 50%, Study Claims

Cheaper fitness trackers were found to be more reliable.

Some popular fitness trackers overestimate the number of calories users burn during exercise, an investigation has uncovered.

The Fitbit Charge 2, the best-selling fitness tracker in the UK, overestimated the amount of calories burned while walking by more than 50%, according to the research led by Aberystwyth University.

It was found to be far more accurate when used to track running through, underestimating the calories burned by just 4%.

The study comes as a separate paper by the Academy of Medical Royal Colleges warns data from fitness trackers can wrongly suggest illness, through inaccurate measurements of heart rate and blood pressure.

The authors say that the NHS may struggle as fitness trackers become more prevalent, because a large number of people “have erroneously been told to attend [treatment] by their AI-enabled Fitbit or smartphone”, according to The Times.

Caiaimage/Chris Ryan via Getty Images

The Aberystwyth researchers analysed the reliability of fitness trackers ranging from £20 to £80 in price for the BBC One Wales show ‘X-Ray’.

Volunteers wore the trackers while running or walking on a treadmill. They were hooked up to an oxygen monitor, so researchers could see how much oxygen they used during each activity and calculate how many calories they burned.

Two of the cheaper devices – by Letscom and Letsfit – were found to be more accurate than the pricier Fitbit when used during walking.

The Letsfit overestimated calories burned by just 2%, while the Letscom overestimated by 15.7% – significantly less than the Fitbit’s 50%. However, the cheaper trackers performed less well with running – the Letscom underestimated by 33% and the Letsfit by 40%.

“If you want to know the exact number of calories that you are burning during an exercise session then it doesn’t matter which device you use, you have to interpret the data with some caution,” lead researcher Dr Rhys Thatcher told BBC X-Ray.

Fitbit told the BBC it was confident about the performance of its product. Letscom and Letsfit said their devices give only estimations and are not scientific devices. HuffPost UK has also contacted the companies for additional comment.

‘X-Ray’ is on BBC One Wales on Monday 28 January at 7.30pm.