Researchers tested popular fitness watches against clinical lab equipment to determine their accuracy in tracking calories burned. The study found that these devices consistently overestimated the number of calories burned during workouts, with error rates ranging from 15 to 25 percent.

The devices tested included Apple, Garmin, Samsung, and Fitbit products. Among these, Apple was found to be the most accurate, while Garmin and Samsung overestimated the most.

Further details about the study and its findings are available, including comments from the study's lead author, who notes the potential for significant discrepancies in calorie tracking.