The higher your body fat percentage, the less accurate your smartwatch is at measuring calories you burn when exercising – new study

Study participants rode a recumbent bike while wearing four smartwatches and breathing into a metabolic analyzer. Taimy Alvarez/Florida International University

Smartwatches have become an increasingly popular way for people to monitor their health and fitness. About 100 million – nearly 4 in 10 – U.S. adults own a smartwatch. Worldwide, market research estimates approximately 560 million smartwatch wearers.

Yet a growing body of research demonstrates that one of the most commonly used smartwatch metrics – number of calories burned – is often inaccurate.