A recent study from Florida International University has raised questions about the accuracy of smartwatches in tracking calories burned during exercise. Researchers compared four popular fitness trackers—Apple Watch Series 8, Fitbit Sense 2, Samsung Galaxy Watch 5, and Garmin Forerunner 955—with clinical equipment used in medical settings. The findings showed that all four devices overestimated the number of calories burned, with the largest errors seen in participants who had higher body fat percentages. The study involved 58 Hispanic adults who completed 10-minute stationary bike workouts at different intensities. To measure the actual calories burned, each participant wore a device called the COSMED K5, which analyzes breath and oxygen use to calculate energy expenditure. The Apple Watch was found to be the most accurate among the four, while Garmin and Samsung watches had the highest overestimation. Fitbit, in some instances, either failed to record data or gave results that were unusually low and not realistic. The researchers warned that these inaccuracies could lead to problems in managing calorie intake. If a person believes they burned more calories than they actually did, they might consume more than intended, leading to a calorie surplus. Jason Kostrna, the lead author of the study, said users should not rely on the calorie counts provided by these devices as precise measurements. He suggested that the algorithms used by manufacturers to estimate calories may be a key reason for the discrepancies. However, the researchers also noted that smartwatches can still be helpful for general health tracking, even with their limitations. The study also pointed out that the data on watch accuracy is still developing, and some results were not included in the final analysis. Kostrna said the next step in the research will be to examine how smartwatches estimate calories burned during strength training exercises. This type of workout may be more challenging for the devices to track accurately, given the different ways the body uses energy compared to aerobic activities like cycling.