Smartwatch calorie tracking accuracy questioned by study

A study conducted by Florida International University has raised concerns regarding the accuracy of calorie tracking in popular smartwatches. Researchers compared the readings of various devices against a medical-grade COSMED K5 metabolic analyzer, which measures exact oxygen and carbon dioxide exchange to determine real energy consumption.

The findings, published in the journal Plos One, revealed that major brands including Garmin, Apple Watch, Samsung Galaxy Watch, and Fitbit exhibited an absolute error margin between 15% and 25%. The study noted that manufacturers' algorithms often overestimate physical effort by processing heart rate and accelerometer data through estimative formulas.

Specific discrepancies included Garmin inflating calorie expenditure by an average of 68.6 calories and Samsung by 56.7 calories. Apple recorded an average overestimation of 21.6 calories. While Fitbit showed a mean error of only 3.14 calories, the device experienced extreme peaks where it reported values up to four times the actual expenditure, reaching as high as 128.6 calories.