Florida International University study finds smartwatch calorie inaccuracies

A study conducted by researchers at Florida International University has revealed significant inaccuracies in how popular smartwatches estimate calorie expenditure. Published in the journal ‘PLOS One’, the research compared the readings of several devices against a professional COSMED K5 metabolic analyzer during stationary cycling workouts.

The study involved 58 participants aged 18 to 50. Results indicated that none of the tested devices were fully accurate, with typical errors ranging between 15% and 25%. While the Apple Watch Series 8 showed the least deviation from laboratory measurements, Garmin and Samsung devices were found to significantly overestimate energy expenditure. Fitbit readings were noted as particularly inconsistent, occasionally providing unreliable or missing data.

A key finding of the research is that accuracy decreases as a user's body fat percentage increases. Researchers suggest that manufacturer algorithms may not adequately account for individuals with higher levels of body fat. Dr. Jason Kostrna, the lead author, cautioned that these figures should not be treated as precise measurements, as overestimations can mislead users attempting to manage caloric deficits for weight loss.