A new Florida International University study found popular fitness watches consistently overestimated how many calories people burned during workouts.
Researchers tested Apple, Garmin, Samsung and Fitbit devices against clinical lab equipment and found error rates often ranged from 15 to 25 percent.
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The study found that Apple was the most accurate. Garmin and Samsung overestimated the most.
"You can't treat the calories burned number it gives you as an accurate number, because it's not," said Jason Kostrna, the study's lead author and FIU associate professor of kinesiology and exercise science in the College of Arts, Sciences & Education. "You could be off hundreds of calories each week and easily end up in a calorie surplus when you think you're in a calorie deficit."
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According to the studies findings, the higher a person's body fat, the greater the errors tended to be.
That means that those who would be more likely to be tracking their calories for weight management may be getting inaccurate information.
Researchers say that while these smartwatches are useful, calorie counts shouldn't be treated as exact.
