Fitness watches can be useful tools for tracking workouts, but a new study suggests users should be cautious about treating their calorie-burn estimates as precise measurements.
Researchers at Florida International University found that several popular fitness watches consistently overestimated the number of calories people burned while exercising.
The researchers compared devices from Apple, Garmin, Samsung and Fitbit with clinical laboratory equipment used to measure energy expenditure.
The results showed error rates frequently ranging between 15 and 25 per cent, indicating that the calorie totals displayed on a person’s wrist could differ substantially from measurements obtained under laboratory conditions.
Apple performed best in the comparison
Among the brands examined, Apple produced the most accurate calorie estimates, according to the study.
Garmin and Samsung devices showed the largest overestimations.
The findings do not necessarily mean fitness watches are ineffective. Wearable devices can still provide users with convenient information about their workouts and help them monitor activity over time.
However, the study suggests calorie-burn figures should be viewed primarily as estimates rather than exact measurements.
That distinction can be important for people who use wearable calorie data to make decisions about how much they should eat, how large a calorie deficit they have created or how much exercise they need to complete.
For example, if a watch reports that a workout burned 500 calories, an error of 15 to 25 per cent could represent a considerable difference between the displayed estimate and a laboratory measurement.
The broader takeaway is that fitness trackers may be most useful for identifying patterns — such as comparing activity levels or workouts over time — rather than treating every calorie displayed as a precise accounting of energy expenditure.
For users trying to improve their fitness, the number on the watch can therefore provide useful context, but it should not necessarily be interpreted as an exact measure of how many calories the body has burned.
