How Many Calories Did You Really Burn?

June 6, 2017

New research from Stanford University and the Swedish School of Sport and Health Sciences has found that if you're measuring how many calories you've burned using a wearable heart rate monitor and fitness tracker --such as the Apple Watch or Fitbit Surge-- the calorie feedback may be way off.

NBC News says six of the seven devices tested produced accurate heart rate readings (within 5 percent.) But even the most accurate fitness tracker was off by an average of 27 percent when it came to measuring energy expenditure. The worst was off by 93 percent!

To put it more simply, if your device suggests you've moved your way through 2,200 calories, on the low end it could be overestimating by as many as 600 calories. The research says the error depends on the type of activity you're tracking. For activities like walking and sitting, the results are more accurate. But for more intense exercises, like spinning and running, you're likely to not be burning as much as you think you are.