Fitness Tracker Accuracy | Pylon Electronics

Have you been tracking your calories and using a fitness tracker to help you lose weight? Struggling with minimal results? You’re not alone and it could be due to the inaccuracy of your fitness tracker.


It seems like almost everyone has tried to lose weight at some point in their lives. Many are in the perpetual yo-yo state of losing, then gaining, then losing, then gaining….and on it goes. But with the explosion of wearable technology that is capable of tracking steps, running, cycling, and practically every form of exercise imaginable, why are 58.1% of Canadians and 68.1% of Americans classified as overweight or obese?


An area that is often overlooked could be that a vital tool many people are using to help them lose weight may be working against them; making it even hard to shred those extra pounds.


A study from Stanford University measured the accuracy of fitness trackers in measuring heart rate and energy expenditure (calories burned). The study evaluated seven different fitness devices — Apple Watch, Basis Peak, Fitbit Surge, Microsoft Band, Mio Alpha 2, PulseOn, and the Samsung Gear S2 — used by 31 women and 29 men. The participants wore their devices while walking or running on the treadmill, cycling on exercise bikes, or sitting still — and none of the devices measured energy expenditure properly.


So how accurate are fitness trackers? They are very good at measuring heart rate but terrible when analyzing energy expenditure or calories burned during an activity. According to the study, the average margin of error regarding the accuracy of fitness trackers measuring energy expenditure was 27.4%. For some activities, the margin of error was as high as a whopping 93%!


Shocked? We were. At Pylon Electronics, we specialize in comprehensive calibration and repair services on a variety of test and measurement equipment. So we’re obsessed with accuracy because it’s at the foundation of everything we do.


Plus, we all assumed that manufacturers test the accuracy of their products, especially when people make lifestyle choices based on their fitness tracker.


What does this all mean? Even at the average of 27.4% margin of error, if you’re fitness tracker reports you burned 500 calories during you last spin class, you probably only consumed 363 calories or even less. A difference of at least 137 calories. Now apply this to a full week and it’s a difference approx. 1000 to 1925 calories, which is significant. This could explain why even when people follow their fitness tracker religiously, there’s little to no difference in their waistline.


A study out of the University of Pittsburgh showed people who use fitness trackers lost less weight than those who don’t. Researchers took 471 people and split into two groups, “Enhanced” and “Standard”. Both groups were given diet advice, counseling, and physical training instruction. The Enhanced Group were given fitness trackers and the Standard Group did not use any technology to help them in their weight loss journey. After 24 months the Enhanced Group lost an average of 7.7lbs, whereas the Standard Group lost an average of 12.98lbs. A difference of 5.28lbs.


Why are fitness trackers so inaccurate? Humans are too varied for an all-encompassing algorithm to measure calorie expenditure accurately. Things like our fitness level, our body composition, and even how we exercise (i.e. our running gait) all make a tremendous difference in how many calories we burn during exercise.


Something else to keep in mind when thinking about calories, as Emma Bryce points out in her TED Ed video, not all calories are equal. Besides the nutritional difference in healthy foods like vegetables over “junk” food like potato chips, our bodies consume calories at various rates.


For example, of every calorie approx. 10% is used for digestion, 20% fuels physical activity, and 70% supports basic functions for things like our organs and tissues. Foods rich in fiber take more energy to digest than foods high in sugar. Your body will burn more of the 100 calories from broccoli during digestion than it will from a Doritos.

If you use a fitness tracker with a goal of shedding a few pounds, be aware of its inaccuracy. It’s fun to capture and visualize the data from all your physical activities and to challenge yourself to burn more calories each week.


However, be aware that you didn’t earn all of the calories that your fitness tracker reported.

Written by Byron Richards for Pylon Electronics.