Have you ever taken note of the calorie burn on your watch only to then grant yourself that allotment for consumption?
Recently I watched Will Tennyson, a popular fitness YouTuber, experiment with this by eating exactly the active calorie output on his watch for two days.
The result? He gained weight!
How can this be, and just what are these smart watching calculating? More importantly, how can we best use the information that is accurate to aid in our health journey?
Recent peer-reviewed studies out of the University of Florida and Stanford have brought to light just how inaccurate smart watches are at calculating active calories. I know; you don’t want to hear this. But trust me, it’s not all bad, and understanding a few key principles will help you use the tool for your benefit and likely even help you with your weight loss goals.
We’ve come to trust, gamify, and even at times obsess over technology. Deep down, we know technology is only a tool, but often we forget that the outputs aren’t real time information. Instead, wearables are algorithms, data points, and estimates.
In addition to Will, others have shed light on just how easy it is to hack active calories via TikTok, YouTube, and Instagram reels that show people throwing the devices in the dryer, hanging them from ceiling fans, and even adding a fast-paced metronome to “speed things up”.
While no one is truly doing this in practice (I don’t think), it does help provide a clue as to how they calculate active calories and why the studies show they aren’t accurate for energy usage.
Stanford University tested the top 7 wearables and found that heart rate and calories burned were anywhere from 40-80% different from the gold standard V02 respiratory devices and ECG’s. Even more concerning is the fact that they tend to overestimate, not underestimate active calories anywhere from 14-23% depending on device. (Fitbit Surge scored best on active calorie burn.)
Why is this?
The reason is in how the technology works and in the limitations of practical use. While the algorithm behind most wearables is slightly different, all of them use a combination of an accelerometer and heart rate to calculate active calories burned.
The problem with this is twofold. First, typically, the wearable is worn on the wrist. What if you are doing a long hold squat or exercise that doesn’t use the arms much?
Secondly, the heart rate monitors don’t always quickly adjust depending on fit to the wrist, sweat, and even positioning. Lotions and even tattoos can impact how quickly your heartrate reads out to current levels.
What can we make of this?
Wearables are a helpful tool, and this post isn’t meant to knock them. They help build healthy habits, track sleep, and are even relatively accurate at capturing your heart rate over the course of time.
The trouble arises when we equate the numbers on the screen to fact and then apply it to our goals, nutrition, and choosing a workout.
Remember that a calorie is a unit of measurement for energy. That’s it!
We can usually tell in the moment what is hard and what isn’t. And remember we lose fat via our breath, sweat, and urine.
If you are breathing hard, sweating, and drinking lots of water you will be losing weight! The more breath you breathe, the more you sweat, and the more you pee, the faster you lose those pesky pounds.
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