How Does A Fitbit Calculate Calories Burned?

Fitbit is a wearable fitness tracker that tracks your daily activities and helps you achieve your goals. The company has over 50 million users worldwide, and one of their most appealing aspects is the calorie count/calorie burned feature. 

How Does A Fitbit Calculate Calories Burned?

This is supposed to track how many calories you burn throughout the day and help you reach your weight loss or gain goal, or your muscle gain goal.

But how does your Fitbit actually calculate this number? And how accurate is it really? Read on to find out more from this informative and well researched article.  

How Does Fitbit Calculate Calories Burned?

Calorie burn is calculated by Fitbit and is based on how many calories you burned throughout the day. It is determined by things such as exercise levels, sleep patterns, and other variables.

Fitbit calculates your daily calorie burn based on the following criteria.

Basal Metabolic Rate (BMR)

This is the amount of energy your body needs to operate at rest. Your BMR is determined by your height, weight, gender, and age. Fitbit uses the personal information you provide when you register your device to estimate your BMR.

The more information you provide, the more precise your predicted BMR will be (so you should fill in not only height, weight, gender and age categories, but also percentage body fat, breathing rate, blood pressure, and heart rate for a more accurate statistic).

This BMR is why your Fitbit app/device will reflect that you are still burning calories even if you aren’t exercising. It takes a lot of energy to simply exist!

Digestion, for example, is a process that takes enormous quantities of energy just to keep the body running. The majority of calories burnt by people are used up just to keep the body at rest, rather than being used by exercise.

Heart Rate 

Your heartbeat is measured by using an accelerometer inside the watch. This accelerometer measures your heartbeat and uses that information to calculate how many calories you burned during your workout.

This data is then synced to your app and your account, where statistics are run and total calories burned are calculated.

A higher heart rate indicates a faster metabolism, whereas having a lower heart rate suggests that metabolism is going at a slower rate, and you are burning fewer calories. 

Daily Steps

All Fitbit trackers can help you see how much you’ve moved during the day. You get an idea of how inactive you were by seeing how long you stayed sitting down.

This helps you understand if you need to change your lifestyle or not – and seeing a very accountable stat about your steps can help to motivate you.

Each step you take is registered, and counted, and then turned into equivalent calories burned. 

Tracked Exercises

Fitbit has a function where you can log exercise into the app – such as swimming, running, roller skating, and even mowing the lawn or cleaning. You should never log an exercise in the Fitbit app if you want to get accurate results.

Your daily calorie count could be inflated by logging an exercise in the Fitbit app. Keeping track of your exercise levels helps the app to make a better estimate of your calorie burn. 

To properly quantify the number of calories burned, Fitbit’s gadgets combine measurements of basic metabolism and breathing, heart rate, physical activity, and sleep habits.

Basal metabolism is calculated by manually entering variables such as sex, age, and weight into the application.

This information is subjected to a complicated statistical algorithm that yields an estimated value. But, since this is merely an estimate, how reliable is this figure?

How Accurate Is The Fitbit’s Estimate Of Calories Burned? 

How Accurate Is The Fitbit's Estimate Of Calories Burned? 

The accuracy of the Fitbit flex and the Actigraph GT3X+ were compared in one study. Individuals wore both of these devices while doing physical activities such incline walking, running, and stepping, and entered all of their height, weight, age, and sex information.

Fitbit’s active energy expenditure was 808.1 calories in this trial, while Actigraph’s was 538.6 calories. When compared to other similar devices, the study concluded that Fitbit has moderate validity and reliability for tracking physical activity.

Participants over the age of 65 were examined using the Fitbit Charge 2 and the Garmin Vivosmart HR+ to compare their accuracy and validity in another similar study.

In comparison to the Garmin VivoSmart HR+, the Fitbit Charge 2 has the highest accuracy and validity. It was also discovered that the Fitbit was more accurate than the Garmin Vivosmart.

When it came to validity, however, both devices produced comparable results; both devices were determined to be successful in monitoring physical activities.

Experts recommend that adults should get 150 minutes of moderate-intensity aerobic activity each week.

This includes anything you do that gets your heart rate up, including walking, biking, swimming, dancing, running, and even yoga and aerobics classes. Moderate intensity means you’re breathing faster but still feeling comfortable.

You won’t feel out of breath or winded after 30 minutes of this type of activity. Fitbit’s activity and calorie trackers can be a really useful component of a healthy lifestyle, through the combination of a lot of different health data statistics.

The estimate isn’t totally accurate – there are so many moving parts and things that a watch cannot pick up on, meaning that some calories are missed, or overcompensated for. However, it is accurate enough to provide guidelines for a healthy lifestyle.

Final Thoughts 

In conclusion, the Fitbit device (in particular, the Charge 2) is a solid fitness tracker with a great design and easy to use interface. It provides a good amount of features and information about your health and well being. 

If you’re looking for a simple device to help you stay motivated and focused on getting fit, that tracks calories fairly accurately without being too bulky or demanding, then we suggest you get a Fitbit.

It may not be perfect, but it certainly gets the job done, and gives you a great baseline. 

We hope that this article has provided insight into the ‘behind the scenes’ process and computations that your Fitbit is doing to conjure up estimates.

Megan Rinzel
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