Smartwatch Alert: Your Calories Burned Walking Is Wrong

Smartwatch Alert: Your Calories Burned Walking Is Wrong

Have you ever wondered how the Apple Watch is counting all your activity calories for you, including calories burned walking? Or your Samsung Gear, or Fitbit, or Garmin? 

The science behind it is actually pretty interesting. In its effort to make a truly accurate calorie tracker, Apple did the largest metabolic analysis experiment in history.

The metabolic profile of approximately 10,000 individuals was measured in Apple’s secret human performance lab in Cupertino, California. The purpose was to create a large set of metabolic information measured by gas exchange metabolic analysis analysis and create correlations with the heart rate and movement data collected by the Apple Watch. 

How Were Calories Measured?

How? The metabolic analyzers measured the caloric expenditure of the test subjects while the Apple Watch measured heart rate and movement. By doing this with several different exercises, Apple trained its watches to estimate the calorie burn for a level of intensity for a person of a specific age, weight and gender. 

Of course you and every one who didn’t participate in this experiment is different from the people who got tested in Apple’s human performance lab. Some of us are actually very different and so the correlations that were built aren’t fully accurate for everyone. So the question that arises is: “How accurate is it?”

Smartwatch Error Analysis – Up to 50% Off

A study conducted at Stanford University evaluated the accuracy of most frequently used wearables.  The study indicated that the Apple Watch has an average error of 30% in its calorie estimations.  

That means that if you get 750kcal of activity calories on your watch you can be anywhere between 525 to 975 kcal. What’s interesting is that 30% is the mean error. The minimum error calculated in the study was 25% and the maximum error was 50%! 

So in the worst case scenario, if your watch is giving you 750kcal you might be anywhere between 375kcal and 1,125kcal.   

Anyone who has dieted can understand how this can completely derail someone’s weight loss attempt.  The goal is to create a reasonable calorie deficit of 500kcal per day that would lead to weight loss of 1-2 pounds per week.  50% errors make it nearly impossible to precisely stay on track. 

However, even though your wearable does a bad job in measuring the absolute number of calories you burn it is still a valuable tool.  That’s because it can track differences between days. 


Calibrate Your Smartwatch With A Metabolic Analyzer

So is there a way to “calibrate our wearable” and make it an accurate calorie counter?

The answer is yes. 

The reason why your wearable is inaccurate is because for any given workout intensity or state of your body (like standing up) the watch estimates that you are burning more or fewer calories than what you really are. 

So if you can measure how many calories you are actually burning and correct your smartwatch’s assumption you should be able to get a fairly good estimate. 

And this is what scientists have now shown! A recent study conducted at Cambridge University showed that by combining a person’s metabolic analyzer data profile with the information collected by a wearable device you can increase accuracy by 4 times during exercise and for your calories burned walking, and by 2 times throughout the entire day. 

Such an increase in accuracy can make your wearable a valuable tool in the quest to lose or manage weight.  It solves the common question of “how many calories did I burn today?” And “Should I trust my smartwatch or wearable for calories burned walking?”

Stay tuned for PNOE’s next smartwatch calibration test where you can see how to read PNOE reports and use that data to adjust a smartwartch or wearable device for counting calories.


Learn About the PNOĒ PrecisionDiet™ Service

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Interested in using the PNOE Metabolic Analzyer for your own business or personal use, to measure and analyze metabolism and to help calibrate smartwatches and wearables?  Get in touch with us below.