Why We Care About Tracking Burned Calories
We all share a common curiosity, whether you’re a fitness beginner or a seasoned athlete: how does your workout impact the calories you burn? Can that extra slice of cheesecake be justified by that intense workout session?
It’s a natural question. If you’re aiming to lose fat, you meticulously track calories consumed and their nutritional value. Similarly, you want to know if your workout burns enough calories to accelerate your progress.
Just like checking the nutrition label on everything you eat, you might wonder: “Is this workout burning a significant amount of calories? Am I effectively tracking burned calories?“
The World of Calorie Trackers
This is where the world of technology steps in. There’s a vast array of devices to help you tracking burned calories – calorie trackers of all sorts. From chest straps to those worn on wrist, belt, arm, ankle, your penis or your vagina (no joke!).
The most common are smartwatches and fitness trackers typically worn on the wrist.
These devices do everything for you: manage phone notifications, track calories burned and steps taken, keep an eye on your heart rate and even monitor sleep quality with several degrees of accuracy.
Wrist-Worn Trackers: Are They Accurate?
But the real question is: how accurate are wrist-worn calorie trackers? Here’s the catch: they’re all using different formulas and algorithm to track your movements and different sensor to track your heart rate and this, specifically, isn’t always perfect and consequently the daily calorie burn estimates – whether during workouts, simple activities like walking, or even just sitting around – can be VERY misleading. Look at it this way:
Your heart is your engine. The higher the demand of energy in your body, the faster it will beat. The faster it will beat, the higher calories you’ll burn provided that you’re doing any kind of physical activity.
On top of that there is proper research looking into actually testing different devices accuracy in tracking burned calories and the results are not too encouraging either:
A 2020 study [source] tested a few known smartwatches brands to find that “None of the tested devices proved to be accurate in measuring energy expenditure“
Understanding Heart Rate Tracking Technology
For instance, most smartwatches have small metallic plates and flashing LED lights on their backs. This technology, called Photoplethysmography (PPG), uses light to measure blood flow.
Smartwatches with optical heart rate monitors use these LEDs to emit green light onto your wrist. Different wavelengths interact with your blood flow in various ways. Sensors then capture this information and translate it into a heart rate reading.
Every company has a proprietary algorithm that then translates these readings into “burned calories“. Since these are not public, it’s not possible to understand why there could be such huge differences between different brands even doing the same activity.
Another study from 2022 [source] tested 3 popular smartwatches brands (Apple, Garming and Huawei) to also find here that energy expenditure (VS a wearable metabolic system used in labs) had quite the margin of difference brand by brand. The study concluded that consumers should be cautious when using the tested smart-watches for prediction of their energy expenditure.
While the process sounds complex, it highlights the key point: those smartwatch lights are crucial for understanding your heart rate. Here’s the simple truth on top of the algorithm secrecy: a restricted blood flow due to improper watch placement can significantly impact data quality. Similarly, activities like cycling or weightlifting, where your wrist is bent, can affect blood flow and compromise data accuracy even more.
Testing Your Smartwatch’s Accuracy
Curious about your smartwatch’s accuracy in relation to your heart rate (HR)? Here’s a simple test: feel your pulse on your neck with two fingers and count the beats for 20 seconds (here is how you do it properly). Multiply that number by 3 to estimate your beats per minute (BPM). Compare this with your smartwatch reading and have an idea of the accuracy of it. You can even do this for a full minute, but it’s easier to lose count over a longer duration.
If you perform this test regularly (like I do), you might discover a discrepancy of 10 to 40 beats per minute between your smartwatch and your actual heart rate, especially during specific exercises. What could this mean? Either your smartwatch is placed incorrectly and can’t measure your HR properly or the sensor it uses is just not that precise.
Should you panic? Nah, in any case these are not medical devices and should be used for reference. This brings us to the next key point.
Inaccurate Calories: Don’t Base Your Diet on Your Watch
Remember, if BPM is a crucial factor in calorie burn calculations, inaccurate heart rate readings translate to inaccurate calorie burn values. More studies comparing gold-standard heart rate measurement with calorie expenditure estimates from various smartwatches (including popular brands like Apple and Samsung) revealed significant discrepancies across all models [Source].
If you’re tracking your daily food calories and you use the “calories burned” to make more space in your diet, you might be ruining your calorie deficit, and might be considerably slowing down your progress.
The takeaway? Be cautious if you rely solely on your smartwatch’s calorie burn data to adjust your diet. Your watch might tell you burned 400 calories, but the reality could be closer to 200 or even 150. Basing your nutrition on smartwatch data is a recipe for disappointment.
Let me share a personal example: I had a smartwatch that would tell me that in a weightlifting session (nothing insane) I had burned a whopping 1400Kcal. If I added those to my basal metabolism rate of 1800Kcal/day, I would have been burning 3200Kcal/day and there was NO way I was eating that much. IF the math was correct I should’ve been shrinking very fast but the reality is that I kept the same size and a stable body weight.
Bottom line? Tracking burned calories and relying on smartwatches to do so, doesn’t bring any useful result.
To lose fat you have to be in caloric deficit through your nutrition, doing more physical activity surely helps and it’s great for your health but forget about the burned calories coming from it.
Using Your Smartwatch Effectively
So, how can you leverage your smartwatch effectively? Consider it a tool to monitor your various health information such as:
- heart rate during activities (even though it’s an estimate)
- number of steps
- sleep quality
but most importantly as a tool to nudge you to be more active.
Being physically active is immensely beneficial for your health and helps your fat loss too. A stronger hearth and cardiovascular system is linked to longer life and better health.
The Fitness Tracker: Your Motivation Buddy
This is my all time favorite aspect of fitness trackers in general: they can be an excellent tool to motivate you to be more active, walk more, and push yourself harder during workouts.
It’s a big deal!
Using your tracker as a tool to push your limits and achieve your daily step goals is a way to add a bit of a self challenge and a game for yourself while focusing on a separate, well-defined nutrition plan for optimal fat loss.
Fine-Tuning Your Nutrition for Fat Loss
Of course, if you’re losing fat too quickly in an unsustainable way, and constantly feel hungry due to intense workouts, you might need to slightly increase your calorie intake. But, again, don’t do it solely based on your smartwatch’s recommendation. Need some help to figure out how many calories you need? check this free calories calculator
Lastly, watch out for this mind-driven red flag: if your brain tricks you into saying “my smartwatch said I burned 500Kcal so I can have this Java Chip Frappuccino” just remember this “it’s just a watch, nothing else” and move on.
Stay strong!