- One study found that the Fitbit Surge had the most accurate calories burned calculation among a group of similar devices, with an error rate just over 25%.
- The other similar devices tested had comparatively higher error rates – up to as much as 93%.
- Still, Fitbits and similar devices are all making an estimate based on your health and activity rate, and their accuracy can vary greatly.
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Fitbits use an algorithm that processes a wealth of data in calculating your calories burned, including information gleaned from your daily activities and about your general health.
But how accurate is a Fitbit's calorie burn calculation?
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Measuring the accuracy of calories burned on a Fitbit
Other similar devices in the study — including the Apple Watch, PulseOn, and Samsung Gear S2 Basis Peak, Microsoft Band, and Mio Alpha 2 — had higher error rates, up to as high as 93%, rendering them more inaccurate when it comes to calculating calories burned.
Essentially, Fitbits calculate calories burned by making an educated guess based on several known factors.
The first is your Basal Metabolic Rate (or BMR) – the rate at which you burn calories at rest to maintain vital body functions – which Fitbit estimates based on your age, gender, height, and weight. Herein lies one problem with the measurement, as not everyone of the same age, height, and weight is going to be at the same fitness level, have the same metabolism, and so on. Already the Fitbit is using generalizations when it runs its calorie burning algorithms
With this baseline data, the Fitbit then uses the activities in which it records you engaging, factoring in your heart rate and motion, as well as activities you manually enter into your profile. All of these data together with your BMR serve to create the estimate of your daily calories burned.
Given all the areas for potential error – including tweaked data input by users and variation in Fitbit models – the accuracy of the calories burned calculation will surely vary.
But at the very least, your Fitbit can still be used as a helpful guideline for planning fitness and weight loss goals.
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