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How Accurate Is Your Fitness Tracker

WEDNESDAY JUNE 15 2016

Nicole MolinFitness trackers are the trendy things right now.  Tons of people have them as part as their daily apparel. In fact, many people have several bands to match every outfit they have.

As fitness trackers continue to trend, I am often asked about the accuracy of these devices, so that’s what we are going to jump into today.

First let me explain what a fitness tracker really is and how it works. Fitness trackers are accelerometer-based monitors that use the body’s acceleration in different directions to estimate energy expenditure. Examples of fitness trackers are Fitbit, Nike Fuelband, Jawbone, BodyMedia, Actigraph, along with many more. Depending on the fitness tracker it either overestimates or underestimates energy expenditure (calories burned) by 10-15 percent.[1]

Now let’s look at what the research says about the accuracy of fitness trackers. We will take a look at the Fitbit since it’s currently the most popular fitness tracker. Columbia University Medical Center researchers found the biggest discrepancy to be when the Fitbit was worn on the wrist during moderate to brisk walking. The Fitbit overestimated energy expenditure by 33.3%-52.4%.[2]  This is huge since moderate to brisk walking is a common form of exercise for people who are looking to lose weight. Your Fitbit is telling you that you burned 300 calories during your daily walk, but in reality you are only burning 100 calories. This information is misleading and can be frustrating if you’re trying to measure how many calories you are burning to reach your goals.

Another factor in the accuracy of fitness trackers depends on the type of exercise. A study published in the Journal of Physical Activity and Health compared the Fitbit to a lab-based method for estimation of energy expenditure for several different exercises. Each exercise was conducted for six minutes. The researchers found the Fitbit either underestimated or overestimated energy expenditure by up to 25 calories. Most exercises the energy expenditure was overestimated, however, cycling and stair stepping was underestimated.[3]  Although 25 calories may not seem like a lot, but if you look at an exercise period of one hour, that’s a 250 calorie error in overestimation or underestimation.

You may be thinking the fitness tracker you have is now junk because the information it’s supposed to track is inaccurate. No worries, there are some good things about fitness trackers. Fitness trackers can be great motivational devices to help you sit a little less and move more. They are also good for you to compare how physically active you are from one day to another. In conclusion, if your fitness tracker motivates you to move more, continue on. However, don’t rely on the information accuracy, especially if you’re counting the calories burned.

Now that we’ve looked at the research, let’s look at the accuracy of several fitness trackers, so you can make an educated decision when purchasing a fitness tracker.[4]

Fitness Tracker       % Error         Calorie accuracy based on 300 calories EE

BodyMedia Fit           9.3%                            272-328

Fitbit Zip                     10.1%                         270-330

Fitbit One                   10.4%                         269-331

Jawbone Up               12.2%                         263-337

Actigraph CT3X         12.6%                         262-338

Phillips Directlife       12.8%                         262-338

Nike Fuelband           13.0%                         261-339

Basis B1 Band           23.5%                         230-371

[1]  Lee, J.M., Kim, Y, & Welk G.J. (2014). Validity of consumer-based physical activity monitors. Medicine and Science in Sports and Exercise, 46(9), 1840-1848.

[2]  Diaz, K.M., Krupka, D.J., Chang, M.J., Peacock, J., Ma, Y., Goldsmith, J., & Davidson, K.W. (2015). Fitbit: An accurate and reliable device for wireless physical activity tracking. International Journal of Cardiology, 185, 138-140.

[3]   Sasaki, J.E., Hickey, A., Mavilia, M., Tedesco, J., John, D., Kozey Keadle, S., & Freedson, P.S. (2014). Validation of the fitbit wireless activity tracker for prediction of energy expenditure. Journal of Physical Activity and Health, 12(2), 149-154.

[4]  Berardi, J. & Kollias, H. (2016). The surprising problem with counting calories. Retrieved on June 13, 2016 from http://www.precisionnutrition.com/cmd.php?af=1588917&u=http://www.precisionnutrition.com/problem-with-calorie-counting-calories-out

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