By Chloe Loukes
Fitness trackers have become popular amongst fitness conscious consumers, with leading brand Fitbit selling over 30 million devices. Trackers are used as a way to see how many steps taken in a day, average heart rate and daily calories burnt.
Researchers at Iowa State University studied the calorie expenditure patterns of eight popular brands of fitness trackers in 60 individuals of varied ages and fitness levels. Subjects completed a 60-minute monitored workout, including 13 different activities ranging from basketball to typing on a computer.
Participants also wore a metabolic analyser, which provided researchers with an accurate calorie expenditure reading.
Results of the study showed accuracy of calories burnt within 8% for sedentary activity read by the tracker. However, alarmingly during strenuous exercise, such as jogging and cycling, the trackers overestimated calories burnt between 10% and 23%. Meaning that while subjects were sitting, the fitness trackers’ calories burnt reading was more accurate than when the subjects engaged in strenuous activity.
Researchers think this is because the trackers don’t account for users’ variance in body composition and factors such as muscle mass, which effects metabolic rate and ultimately, calories burnt.
Fitbit issued a statement in response to the study claiming, “their trackers are not intended to be scientific or medical devices and are instead designed to provide meaningful data.”
Euan Ashley, medical professor at Stanford university commented, “People are basing life decisions on the data provided by these devices”.
Many consumers rely on information from these devices as a means to determine their calorie intake, so these inaccuracies could be hindering progress by telling users they are burning more calories than they actually are, and as a result, they are allowing themselves an extra glass of wine or bowl of ice-cream.