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Are Fitbits Accurate? How Relevant is Accuracy For Fitness Activity Trackers?

Let’s say you are looking for a trustworthy fitness tracker. Of course, there are plenty of offerings on the market, from manufacturers like Apple, Samsung, Fitbit and Garmin. You may be wondering which one is worth buying and after doing some research you decided to go for a Fitbit health tracker. However, the question that is still lingering is: are Fitbits accurate? If so, how can we determine that?
In order to help you make a conscious and informed decision, we’ll try to asses how accurate are Fitbits and whether Fitbits are worth buying.

At some point in 2019, researchers at Aberystwyth University have been testing the accuracy of popular activity trackers for a BBC Wales consumer affairs program, and Fitbit was among the devices experimented with, precisely Fitbit Charge 2.

The test consisted of participants walking on a treadmill for ten minutes at 4km per hour, followed by a ten-minute jog at 8km per hour. The amount of oxygen used during their activity was monitored and
Dr. Rhys Thatcher concluded that “There is a direct relationship between the amount of energy somebody is using and the amount of oxygen they are burning. If you know how much oxygen you’ve burned, we can then know accurately how many calories you’ve expended throughout the activity.

So what does this mean in relation to how accurate are Fitbits? According to Dr. Thatcher the precision of activity trackers is not that important when looking at their health benefits. Confused?

Although activity trackers certainly have a role to play in improving health, Dr. Thather thinks ‘you have to interpret the data coming out of them with care – they are not direct measurements.
Furthermore, the study focused on the fact that Fitbits, as well as other fitness trackers, are useful when tracking progress and can be a great motivational tool to help people to maintain motivation to exercise.

Therefore, ‘activity is one of the biggest determinants of health’, he concluded.

The International Journal of Environmental Research also concluded that what you’re doing will affect how accurate your tracker is when estimating TTE and while “mainstream devices are able to reliably measure heart rate, number of steps, distance, and sleep duration, which can be used as effective health evaluation indicators, the measurement accuracy of energy consumption is still inadequate. Fitness trackers of different brands vary with regard to the measurement of indicators and are all affected by the activity state, which indicates that manufacturers of fitness trackers need to improve their algorithms for different activity states.”

While all trackers work with your personal data, referring to height, weight, gender, and age and metrics like basal metabolic rate or BMR, it also considers the speed with which people burn calories consumed in resting mode. As you can notice, there are some things to consider, as well as keeping in mind that the experience is slightly different for each individual. For example, an elevated heart rate doesn’t necessarily translate into an intense jogging session as it may well be the response to a stressful situation.


That being said, perhaps the question is whether focusing on how accurate are Fitbits is not the point of the gadget’s value or functionality. After all, it’s all about perspective.

Although not 100% accurate – no fitness tracker really is – Fitbit health trackers are excellent at getting you to move more, as they measure steps, distance and calories burned and the amount of activity during the day so that you can track your progress over time. Naturally, following your progression will motivate you to set goals and better perform.

So, can you trust it? How accurate is the Fitbit Fitness tracker

In search of a reliable health tracker, people flock to the offerings of Apple, Samsung, Fitbit or Garmin. These brands – and not just them – have amassed quite a number of fans and good reviews. But exactly how trustworthy are they? How accurate is Fitbit, for example, when it comes to calories tracking?

Things are not as black and white as we’d want them to be. There are several indicators Fitbit uses to track calories burned and it’s those that you should know well before drawing any conclusions.

How Accurate is Fitbit When It Comes to Calories Burned?

Simply put, Fitbit trackers are not 100% accurate – but no commercially available wearable now is.

If you want numbers, we can tell you that back in 2019, a study found Charge 2 to be very accurate at estimating calorie burn during jogging – under predicting by 4.3% – and less accurate during walks, when it overestimated calories burned by 53.5%.

Why is that?

We know that sometimes you can start doubting if the tracker results are accurate or there are some problems with your Fitbit devices, particularly if you aren’t managing to hit your goals.
Before you start to troubleshoot Fitbit to try to get perfect accuracy, you have to understand how Fitbit calculates calorie burn to begin with.

Just like Apple Watch, the tracker starts from your personal data, info that you input from the get-go. That refers to height, weight, gender, and age.

Then, it looks at your basal metabolic rate or BMR. This takes into account the speed with which people burn calories consumed in resting mode, so effectively calories burned while you’re doing nothing.

To this, Fitbit adds possible activities it detects by taking into consideration heart rate and/or motion. Only an elevated heart rate doesn’t necessarily translate into a hearty jog session as it may well be the response to a stressful situation.

The motion could be a nervous tick like moving your leg up and down when you’re extremely excited.

Fitbit doesn’t make any difference – on paper – between “active calories” and “resting calories” (BMR). It also can count as movement things like fussing with your gadget strap along your wrist.

Nevertheless, another 2017 study published in the Journal of Personalized Medicine found that the Surge model from Fitbit had back then just a 27% margin of error, the lowest among the devices tested which included Apple Watch, Gear S2 and others.

HOW ACCURATE IS APPLE WATCH CALORIES? 

Apple Watch Series shows you total calories, including active ones (AMR) by subtracting the basal (resting) ones from the total measured.

There are studies concluding that Apple Watch is one of the best in its class out of 60 other competitors for energy expenditure tracking.

There are ways to improve the accuracy on Apple Watch Series, if you choose to go with one.

Fitbit vs Apple Watch: Which is More Accurate at Calories Burned?

It’s really hard to say but there are a couple of things you should take into consideration.

First, Apple does differentiate between “active calories” and “resting calories”, unlike Fitbit. So, if you’re adamant to know exactly how many calories you’ve burned while doing exercise, Apple Watch should be a bit more accurate.

If you don’t care and just want a rough estimate, Fitbit trackers are good enough.

Also, Fitbit starts measuring your calories at midnight and it only shows the total burned calories, without making the distinction between them. So, calories while sleeping will also be added to the total you see in app or on the watch face.

Most Accurate Calories Tracker

Now, most wearables rely on the criteria we talked about above. So all of them will give you an estimate of the calories you burned, depending on the algorithms used.

Some will rely more on heart rate, while others will take in accelerometer data. “Depending on which method that company or device follows, you could get quite different energy-expenditure estimates.” said Andrew Jagim, PhD, director of sports medicine research at Mayo Clinic Health System, for NY Times.

Wearables such as fitness trackers or smartwatches do not compare with medical devices. It’s not surprising that the most accurate calorie burn tracker out there isn’t one of those.

Instead, it’s a leg wearable developed by a Stanford University graduate student. By being worn on your leg than wrist, it can track the actual movements of your legs and not confuse it with a clap or wave.

Plus, it has two sensors, a hip pack, wires, and straps. Admittedly, it’s not the sexiest health accessory out there for the regular consumer. Its creator intends to make a smaller and lighter version though, which could go inside a piece of clothing and use a phone as a controller in the future.

Until then, if you’re curious to see how much better is this leg wearable, you can build your own. The developer uploaded the instructions and code online.

Otherwise, you might look into alternative methods of keeping up with your health progress.

Set small goals, start a food diary and make sure you stay on top of your fitness game by adding workouts to your calendar and creating reminders for them.

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Are Fitbits Accurate? How Relevant is Accuracy For Fitness Activity Trackers?
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