Dr. Friedman’s Health Blog

Your Fitness Tracker is LYING!

By: Dr. David Friedman

Over 40 million people in the United States have smartwatches or fitness trackers to help them get in more steps throughout the day,  improve their heart health, burn off calories and lose weight.  But just how accurate are they? Before you brag to your friends that you achieved your 10,000 steps quota for the day because your Fitbit says so, you may be surprised to learn…


Unfortunately, these wearable fitness devices will not accurately count your steps. Research conducted in 2019 showed that they are  40.1% inaccurate!  In 2018, another study conducted by the University of British Columbia, showed the accuracy of fitness trackers to be even worse! They found these devices have a 50-50 chance of getting the step counts right.  That means, if you think you’ve walked 10,000 steps, in reality, you may have only walked 5,300!

The number of steps taken from these devices really comes down just a guestimate.  Even the official Fitbit Community Forum is overflowing with complaints from users on the inaccuracy of Fitbit’s ability to count steps. The same complaints can be found regarding the Garmin and the Apple Watch.   There are a few reasons why  these devices are so lousy at counting steps. First, they also track movements not associated with walking. For example, washing your hands, ironing clothes, preparing food, petting your dog, or using a computer mouse can result in steps being registered by your device. Also, walking with your arms by your side or just moving them slightly will register as if you’re not walking.  I’ve always wondered why these trackers aren’t designed to be worn on your ankles instead of your wrist?  But on second thought, if you have restless leg syndrome or tap your toes while listening to music, having this device on your ankle could register as if you just ran a 10K.  

Another issue is the inaccuracy between different trackers.  For years, I’ve had patients ask me which brand is the best?  And one day,  I decided to put the two most popular wearable fitness trackers (the Apple Watch and the Fitbit) to the test. While wearing both of these devices, I tracked how many steps I took during an entire day.  The results showed the Fitbit registered 1,610 steps less than the  Apple Watch. That’s a big discrepancy! 



It’s not just a matter of miscounting steps;  these devices also do a lousy job of monitoring your heart rate. Unfortunately for some, this could be a serious health risk.  Many heart patients rely on these wearable fitness devices for medical monitoring.  Several class-action lawsuits have been filed against Fitbit for “consistently mis-recording heart rates by a very significant margin.” 

There have been several different studies showing fitness trackers and smartwatches are better at measuring heart rate accurately while at rest or in recovery, but get less accurate as the intensity of exercise increases. The reason for this is, as you sweat during exercise, the sensor can fail to record your heart rate due to poor conductivity.

Another reason the heart rate monitors aren’t  effective  is because most of them rely on green lights. These lights are cheaper to use and less accurate than the infrared lights that power hospital-grade heart rate trackers.  Also, skin with more melanin blocks green light, making it harder to get an accurate reading. That means, the darker your skin, the less accurate the devices become.  Caucasians that are tan, Hispanics and black people are more likely to have false readings on their heart rate trackers.   People with a heart condition should be very cautious about relying on these wearable heart rate monitors.


So, you think you burned 600 calories during spin class? Sorry to burst your bubble but if you’re relying on a wearable fitness tracker to accurately tell you how many calories you burn, don’t believe it!  

In 2015, the Journal of Physical Activity and Health examined Fitbit’s calorie-burning accuracy. After participants went through different physical activities, including raking, walking up stairs, golfing, and carrying various items, they concluded that the Fitbit “significantly underestimates” calorie burning.   The activities that the Fitbit gave an especially low, inaccurate number included cycling, sweeping,  raking, and walking on a treadmill. 

In another study published in 2017 by published in the Journal of Personalized Medicine, they found that Fitbit had a 27% margin of error when measuring calories burned.  That was actually better than the other brands they tested. The Apple Watch, PulseOn, and Samsung Gear S2  Basis Peak, Microsoft Band, and Mio Alpha 2 — had as much as a 93% inaccuracy rate when calculating calories burned. To put that into perspective, if your device shows you’ve exercised your way to burn off 2,000 calories, on the low end it could be overestimating this by as many as 700 calories.  So if it appears as though you’ve burned off that entire Big Mac, fries and coke you had for lunch,  in reality   you only “earned” those fries.  You simply can not base the number of calories you eat by how many calories your device says that you’ve burned.

One  reason these wearable devices are so inaccurate when it comes to counting how many calories you’ve burned is they don’t take into consideration your fitness level or whether you’re leaning on the handlebars of that elliptical or using your body weight during the downward push of a stationary bike. These things can impact your energy expenditure. Also, these devices don’t take into consideration your fitness level.  If you are just starting an exercise program, the newer you are, the more calories you will burn. As someone becomes more proficient at a certain exercise, they will burn fewer calories doing the same activity for the same period of time. Another consideration these wearable trackers don’t take into consideration is body composition.  At first, people have more fat than muscle mass which means they will burn fewer calories when first starting an exercise regimen. As they build muscle, their body becomes more efficient and will burn more calories for the same amount of exercise.  In addition, body size is also not accurately tracked. Someone with a large frame or “big-boned” won’t burn as many calories as someone who stores a lot of fat.  



I’m actually not a fan of focusing on calories as a basis for eating or exercising. Counting calories has become the standard methodology for people wanting to lose weight but what exactly is a calorie? By definition, a calorie is a measurement of heat. It’s the amount of heat required to raise the temperature of one kilogram of water through one degree Celsius. A calorie is heat! If heat caused weight gain, everyone living in the southern hemisphere would be obese but they are actually leaner

When comparing a 100-calorie apple with a 100-calorie pack of cookies,  to view them as being the same makes no sense. No one has ever gotten obese from eating too many calories of apples. In fact, if you were to eat just apples for two days and then compare this with two days of just eating the equivalent amount of calories in cookies, I guarantee you will have lost weight eating those apples compared to the two days of eating just cookies.  

Tracking how many calories you burn also means having to become a mathematician and that takes the enjoyment out of eating and exercising. I believe instead of counting calories; you should make your calories count!   Eat  primarily wholefood plants, lots of fiber and lean organic  protein like fish, eggs or chicken.  On my syndicated show To Your Good Health Radio, I’ve had the privilege of interviewing many of today’s leading celebrity fitness experts including Denise Austin, Richard Simmons, Donovan Green (Dr. Oz’ personal trainer,)  and Jay Cardiello (TV celebrity trainer.)   I have asked them all the same question:  “What percentage of weight loss is exercise vs. diet?”  They all agree, losing weight is 80% diet and 20% exercise. You lose weight in the kitchen and you get trimmed at the gym.  Focus on movement, increasing your heart rate and eating clean and you don’t have to play the calorie counting game.


These wearable fitness trackers aren’t accurate. So what?  With the exception of a heart patient relying on heart rate accuracy, the goal is to get active and move!   If these devices give you a sense of accountability, more power to them!  It’s better than sitting on the couch watching TV, playing games or surfing the internet.   Sitting is the new smoking and evidence shows sitting can kill you!  In fact, too much sitting is a contributing factor to heart disease, stroke, diabetes, kidney disease, clinical depression, COPD (such as emphysema),  liver disease, peptic ulcer, Parkinson’s disease, Alzheimer’s, musculoskeletal disorders and cancer~!

Most of these fitness wearables have a “sedentary warning,” which pings when you’ve been sitting on your ass for too long.  Fitness experts say having a friend to exercise with will help you stay motivated to exercise.  These fitness wearables, accurate or not,  offer people a great virtual work-out buddy.

About the Author

Dr. David Friedman is the author of the award-winning, #1 national best-selling book Food Sanity, How to Eat in a World of Fads and Fiction. He's a  Doctor of Naturopathy, Chiropractic Neurologist, Clinical Nutritionist, Board Certified Alternative Medical Practitioner, and Board Certified in Integrative Medicine.  Dr. Friedman is a syndicated television health expert and host of To Your Good Health Radio, which has changed the face of talk radio by incorporating entertainment, shock value, and solutions to everyday health and wellness issues.

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