Smartwatches Overstate Calories Burned by 15–100% Depending on Body Fat

A Florida International University study tested Apple, Garmin, Samsung and Fitbit watches on 58 adults: three of four devices overstated calorie burn by 15–25%, with errors reaching 50–100% for users with higher body fat. At 35% body fat and four hours of weekly exercise, the gap can hit 1,200–2,400 calories per week.

• Three of four brands overstated calories burned by 15–25%
• Error reached 50–100% or more at higher body fat levels
• Weekly gap can total 1,200–2,400 calories
• Heart rate tracking was found to be fairly accurate