How Accurate Is Fitbit Calories Burned?

Heath tracking devices are one of the most popular fitness crazes of the 21st century. They’re so ubiquitous that they’ve become part of our culture — you can find them in offices, gyms, bedrooms, living rooms, and kitchens across America.

How Accurate Is Fitbit Calories Burned?

And while many people love using these gadgets to monitor their health, there are also plenty who have concerns about what data they collect, and if it’s even accurate.

Most fitness trackers will cover the same ground, and record things like daily step count, heart rate, hours in deep sleep, and the topic of our discussion today; how many calories have been burned.

The FitBit is one of the household names of the fitness device world, and we wanted to research whether they are as accurate as they say they are. Let’s take a look.

Is A Fitbit Device Accurate?

The short answer is that no fitness device is going to be 100% accurate, and there are many factors that determine how many calories are expended per day that goes beyond the ability of a wearable device to detect.

According to several studies carried out with a Fitbit, they are more accurate than competitive devices on the market.

Although, when they do show some inaccuracies, they can be out by as much as 50% which is a lot in the grand scheme of things. This could be the difference between an extra meal per day for some people.

In one study carried out in 2017, the FitBit Surge was shown to have a median error of around 27% when counting calories that had been burned throughout the day. (Source)

The most surprising thing about his finding is that it was still more accurate than some of the other models on the market including the Apple Watch, Microsoft Band, and the Samsung Gear S2.

The limitation with this study is that it was carried out in 2017, and fitness devices have advanced since then, right?

Well, a 2019 study found that the FitBit Charge 2 over two years later still overestimated calories when walking, and this increases the average to around 53%.

What offsets this discrepancy is that during a jogging phase, the device was much more accurate – at only around 5% inaccurate which is a stark difference. (Source)

Does this mean that Fitbit devices are more accurate only when during activity? This may be a problem as not everyone is jogging all of the time and most of our lives are spent at a lower intensity. At least it likely is anyway!

Why Fitbits Might Not Be Accurate

How Accurate Is Fitbit Calories Burned?

There are many reasons why a Fitbit cannot accurately predict how many calories you are burning throughout the day.

The first reason is that Fitbit doesn’t know how you are exercising and doesn’t factor in that everyone is at a different fitness level.

Let’s say you’ve gone for a run on an Elliptical machine. Are you leaning on the handlebars, and is your resistance level on a low setting?

It’s incredibly hard to predict how many calories are burned during exercise because everyone will expend a different amount of energy.

Being more overweight is going to change how many calories you burn, just as how effective you are at a certain sport or exercise will.

This is similar to Fitness tracking apps that allow you to input an exercise session you did, which then takes off calories you have burned throughout the day.

The problem with this method is that how can you tell if the person worked hard or not, or whether they gave it everything?

A casual 60-minute Basketball with your buddies in a local park is going to be different from a 60-minute Basketball session carried out by Michael Jordan in his prime. Yet, both are expected to burn the same calories?

Further to this is the notion that we have to be exercising to burn calories. Yet, we forget that we are burning calories all the time and that it doesn’t just shut off when you start up a treadmill. These intricacies are hard to track in a real-life setting.

Another factor to consider is that we all eat different diets and different food groups cost more energy to digest and absorb than others.

For example, the thermic effect of protein is around 30%, meaning 30% of the chicken breast you consume is burnt for energy.

Whereas dietary fat is around 5%, a person eating a higher protein diet will have a much higher calorie burn rate than a person who doesn’t.

Should You Use A Fitbit If It’s Prone To Inaccuracy?

How Accurate Is Fitbit Calories Burned?

This leads us to a bit of a conundrum: should Fitbits be used if they are prone to inaccuracy?

It’s a good question, as we are potentially derailing our progress. This is especially relevant for those that are trying to lose some weight, as calories will determine whether we maintain, lose or gain weight in the first place.

Being out by over 50% will potentially wreck somebody’s progress because they think they are burning more calories than they are.

This means they believe they can eat more food when in reality they can’t and will struggle to figure out why they are not losing weight.

Given the discrepancies that come with calorie trackers, it’s best not to treat the calorie counter as the be-all-end-all. If calories are important for your goals you are better off tracking what goes in your body as opposed to what is expended. 

This is because you have much better control over knowing what foods you are eating and how many calories are in those foods.

However, we wouldn’t recommend throwing out your Fitbit either, as they still have many great functions that can help you with your fitness goals. See them as a supplement as opposed to the holy grail of results.

Final Thoughts

Calorie counters are useful tools but they aren’t always 100% accurate. The bottom line is that calorie counters are a tool and not the be-all-end-all to help you achieve your goals!

Megan Rinzel
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