Overview
- A peer-reviewed study released Wednesday by Florida International University compared four mainstream watches to a COSMED K5 metabolic analyzer in a controlled lab test.
- Researchers had 58 adults ride a recumbent bike while wearing one watch each and measured true energy use by gas exchange, the clinical gold standard for calories burned.
- Across devices the typical calorie-estimate error was about 15 to 25 percent, with some models showing larger average deviations from the metabolic measure.
- Brand patterns emerged in the test: the Apple Watch was most accurate, Garmin and Samsung tended to overestimate calories, and Fitbit produced repeated glitches that required filtering.
- Authors warn users to treat smartwatch calorie totals as an upper bound, rely more on heart-rate metrics and trend tracking, and note the team is running follow-up studies on other workout types.