Smartwatch calorie tracking accuracy challenged by new study

A study conducted by Florida International University has revealed significant discrepancies in how popular smartwatches estimate calories burned. Researchers compared the readings of an Apple Watch Series 8, Fitbit Sense 2, Samsung Galaxy Watch 5, and Garmin Forerunner 955 against a COSMED K5 metabolic analyzer, which measures actual energy expenditure through respiratory gas exchange.

The findings indicated that Apple was the most accurate device among those tested. In contrast, Garmin and Samsung tended to overestimate caloric expenditure, with median absolute percentage errors generally ranging between 15% and 25%. Fitbit's data was partially excluded from the analysis due to readings that were either inconsistent or implausibly low.

Lead author Jason Kostrna warned that users should not treat smartwatch data as exact figures, as relying on these estimates for weight management or dietary adjustments could lead to unintended caloric surpluses. The study also noted that deviations were more pronounced in individuals with higher body fat percentages.