how does fitbit track calories burned

Monitoring individual physical activity is an effective and important method to promote a healthy lifestyle. How does Fitbit track calories burned? Fitbit tracking devices measure both physical activity and health statistics, such as oxygen saturation, step count, heart rate and calories burned. 

Fitness trackers have become increasingly popular as both, science and technology, continue to evolve in the 21st century. The company, “Fitbit Inc” from California, USA holds 20% of the market share value for wearable tracking technologies. Fitbit Inc. sells a variety of different products including fitness trackers, smart scales and smartwatches. Fitness super watches like the Fitbit Surge, have an integrated GPS, a touchscreen monitor and wireless syncing.

What are calories and why do they matter? 

Calories are a measurement of energy. Calories are essential for the metabolism of the basic functional macromolecules. When food begins to break down, it releases this energy which may be used immediately or stored for later. The intake of calories from food nourishes the body’s cells with the energy required to perform daily tasks such as thinking, walking, and talking. 

The intake of excessive amounts of calories may lead to obesity. Obesity is a growing problem, particularly in Western societies, increasing the risk of chronic disease. In addition to helping maintain a healthy weight, studies show that restricting calorie intake can reduce the risk of Alzheimer’s disease, oxidative stress, and cancer. 

Factors such as gender, age, weight and height can affect daily caloric intake needs. For example, women on average should limit themselves to 1500 calories to lose 1 pound per week. Whereas men require 500 more calories to lose 1 pound per week. These averages vary depending on age, weight, and height. 

 Physical activity encourages daily calorie burn. Eating healthy and staying active can help individuals with obesity lose weight and maintain a healthy body weight. 

How does the technology work?

Most fitness tracking devices are worn on the wrist. Why? In comparison to other places on the body, the wrist serves both comfort and user-friendliness. 

Fitbit devices are wrist-worn technologies that use a triaxial accelerometer to measure body motion in 3D space. The device uses algorithms to measure step count, heart rate, calories burned, basal metabolic rate, and sleep.

Step count is measured by a sensor that responds to elevation (1 floor = 10 feet). Fitbit does not count steps from walking down a flight of stairs or exercising on the “StairMaster.”

Capillaries expand and contract when the heart beats. Heart rate is measured by another sensor in the Fitbit that responds to volumetric changes in the capillaries of the wrist. This feature is especially useful when determining the intensity of a workout or exercise. 

How does Fitbit track calories burned?

Fitbit devices integrate measurements of basal metabolic rate and of breathing, heart rate, and other daily physical activity data to accurately measure the number of calories burned. Basal metabolic rate is calculated from manually logging data into the app such as sex, age, height, and weight.

One study compared the accuracy of Fitbit Flex and Actigraph GT3X+. Individuals wore both these devices while performing activities such as incline walking, running, and stepping. Activity energy expenditure from Fitbit was 808.1 calories while the Actigraph was 538.6 calories. The study concluded that Fitbit overall does have moderate validity and reliability for measuring physical activities.

Participants over the age of 65 participated in a study comparing Fitbit Charge 2 and Garmin vivosmart HR+. The results varied widely but the Fitbit showed the best results in terms of accuracy and validity, in comparison to the Garmin. 

Fitbit and other wearables provide a way to track the number of calories burned through physical activity by combing various health data. Even though technology may have its flaws, the Fitbit calorie estimate is an overall helpful tool in determining the next steps to a healthy lifestyle. 

Experts suggest that adults should be getting at least 150 minutes per week of physical exercise. Intense exercises are not a necessity for weight loss or burning calories. Walking, riding a bike to work or taking the stairs are simple activities that can increase calories burned and boost overall health.

Fitbit and Mental Health

When considering physical health, it is just as important to consider mental health. One study examined the approach of Fitbit use in therapy for post-traumatic stress disorder in veterans. Veterans were asked what motivated them to use or not use the Fitbit during their treatment. Increase of self-awareness, promoting social interactions and supporting other veterans were the three motives for Fitbit use. Unable to understand the purpose and data of Fitbit and its issues in the veteran-provider relationship were motives to avoid Fitbit.

Fitbit and other wearable technologies have the potential to serve (alongside many other therapeutics) in the treatment and management of mental health programs. 

References:

Fitbit – https://www.fitbit.com/global/us/home

Feehan, L. M., Geldman, J., Sayre, E. C., Park, C., Ezzat, A. M., Yoo, J. Y., Hamilton, C. B., & Li, L. C. (2018). Accuracy of Fitbit Devices: Systematic Review and Narrative Syntheses of Quantitative Data. JMIR mHealth and uHealth6(8), e10527. https://doi.org/10.2196/10527

Lewis, Z. H., Pritting, L., Picazo, A. L., & JeanMarie-Tucker, M. (2020). The utility of wearable fitness trackers and implications for increased engagement: An exploratory, mixed methods observational study. Digital health6, 2055207619900059. https://doi.org/10.1177/2055207619900059

Sushames, A., Edwards, A., Thompson, F., McDermott, R., & Gebel, K. (2016). Validity and Reliability of Fitbit Flex for Step Count, Moderate to Vigorous Physical Activity and Activity Energy Expenditure. PloS one11(9), e0161224. https://doi.org/10.1371/journal.pone.0161224

Osilla EV, Safadi AO, Sharma S. Calories. [Updated 2020 Aug 25]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK499909/

Yang Y. J. (2019). An Overview of Current Physical Activity Recommendations in Primary Care. Korean journal of family medicine40(3), 135–142. https://doi.org/10.4082/kjfm.19.0038

Ng, A., Reddy, M., Zalta, A. K., & Schueller, S. M. (2018). Veterans’ Perspectives on Fitbit Use in Treatment for Post-Traumatic Stress Disorder: An Interview Study. JMIR mental health5(2), e10415. https://doi.org/10.2196/10415

Tedesco S, Sica M, Ancillao A, Timmons S, Barton J, O’Flynn B
Validity Evaluation of the Fitbit Charge2 and the Garmin vivosmart HR+ in Free-Living Environments in an Older Adult Cohort
JMIR Mhealth Uhealth 2019;7(6):e13084

Image by Vidmir Raic from Pixabay 

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