November 13, 2018
Young black woman in a forest checking smartwatch and smiling
Wellness Tip

How Accurate Are Fitness Trackers?

by Berkeley Wellness  

Don’t count on wearable fitness trackers to accurately measure your energy expenditure—their results vary widely and may differ significantly from laboratory measurement, according to a small Japanese study published in JAMA Internal Medicine.

The researchers tested 12 leading devices in 19 healthy adults, ages 21 to 50, and found that they differed in their estimates of daily energy expenditure by as much as 500 calories. Compared to the results of one gold-standard test (called the double-labeled water method), the devices all underestimated daily calorie expenditure. But compared to another type of validated testing (done in a metabolic chamber), about half of the devices underestimated, while half overestimated daily calories.

None of this may matter much for typical users, who may still be motivated by the devices. And as long as the devices are consistently inaccurate, they can track progress over time. It’s probably better that the devices underestimate than overestimate—if people are told they are burning more calories than they really are, they may use that as permission to exercise less or eat more.

Also see Fitness Trackers vs Smartphone Apps.