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Smartwatches overestimate calories burned during exercise, study finds

Researchers at Florida International University observed error margins of 15% to 25% across four popular wearable brands.

The short version

  • A Florida International University study found that popular smartwatches systematically overestimate energy expenditure during workouts.
  • The tested devices averaged a 15% to 25% margin of error compared against standard metabolic measurement tools.
  • The Apple Watch Series 8 exhibited the smallest margin of error, while Samsung and Garmin devices showed higher rates of overestimation.
  • Researchers noted tracking accuracy declined as participant body fat increased, though the underlying cause remains undetermined.

Key facts

  • A study conducted by Florida International University tested calorie-tracking accuracy across 58 participants using an Apple Watch Series 8, Fitbit Sense 2, Samsung Galaxy Watch 5, and Garmin Forerunner 955.[CNET]
  • Participants exercised on a stationary machine while wearing the smartwatches alongside an electrocardiogram chest strap and a Cosmed K5 energy-measuring device.[CNET]
  • The tested smartwatches exhibited an average margin of error between 15% and 25%, consistently overestimating calories burned.[CNET]
  • The Apple Watch had the smallest margin of error among the models tested, while Samsung and Garmin models exhibited higher levels of overestimation.[CNET]
  • Data from the Fitbit Sense 2 was partially excluded by researchers due to technical glitches encountered during testing.[CNET]

What remains uncertain

  • The physiological or technical reason why smartwatch tracking accuracy degrades as a user's body fat increases has not been determined.[CNET]

Sources