A lot of us have used our smart watches’ of fitness trackers’ “calorie burn” feature – or at least looked at it, right? Whether you’re looking at your total daily “burn” or how many calories you torched during your workout, chances are that if you own a watch with this capability, you’ve seen this number and thought about a few things, like…

• If my watch says I burned 240 extra calories does that mean I need to eat 240 extra calories later?? Or does that put me in a greater deficit?
• Oh wow, that was a good workout!
• Oh wow, that workout was useless.
• Awesome, I can have the cookie now!
• Man, I guess I won‘t be able to get drinks later.
• I need to burn 100 more before I leave so I can go out with my friends.

All thoughts & questions that makes sense and I have asked myself, too. And I know this is a bummer to find out, but your $300 watch or fancy Fitbit is trash at estimating your calorie burn. (But it’s not totally useless, so stick with us here.)

Let me tell you this first: I LOVE my Garmin watch. I have a Vivo Active 4 and it’s great. I don’t wear it everyday – mostly because I find it a little distracting while I’m trying to work – but I love wearing it if I notice I’m being more sedentary during my days, if I’m going on a run, and particularly when I’m hiking. I love that it can count steps, flights climbed, pace, miles covered, etc. And I think it has some crazy awesome features. And I know a lot of people who love their Apple Watches and FitBits.

But the biggest reason using the “calories burned” feature is honestly useless on most watches like this is because it’s just straight-up pretty dang inaccurate.

We’re talking like 40-80% inaccurate.
That’s a lot.

For some people, it will way overestimate calories burned.
For others, it will way under-estimate calories burned.
Not just based on the person wearing it, but the activity they’re doing.

So if these watches are so “smart,” how (and why) are they so off on their estimations?

Your watch or fitness tracker likely uses a formula that accounts for your heart rate (and sometimes bodyweight & height) to estimate how many calories you burned during an activity. The problem?

Metabolism is WAY more complicated than that.

Your fitness tracker simply CANNOT account for your body composition, current fitness level, habits, recent nutrition & macro make-up, stress levels, hormone levels, metabolic history, genetics…
Don’t believe me? Let’s take a glance at a graph showing how metabolism really works with a metabolic pathway illustration.

Metabolism is a complex thing (um, clearly). Do we need to understand this entire chart to have a fairly decent understanding of metabolism overall? No. But when you begin to try estimating caloric burn from heart rate alone, you’re probably not going to get a super accurate (or helpful) answer. So let’s take a step back and look at what we should know about our metabolism.

Basically, the calories that we’re all fretting over- the calories we burn during exercise – come from that little guy at the top. This guy is called EAT (funny, right?) which stands for Exercise Activity Thermogenesis – the amount of energy your body expends during formal exercise. This is the least-energy-consuming aspect of your metabolism in the grand scheme of your day.

I mean, think about it:
Say you spend 1 hour working out. The other 23 hours are going to add up to a lot more calories burned than the single hour you spend a little more active than the rest.

This is because your body uses a heck of a lot of energy to literally just function and survive, which is pretty cool if you ask me. More on metabolism in a separate post.

Okay, so now we’ve established that the watch isn’t accurate to estimate calories burned…

But, if that’s the case, how do we know if we’re getting in good workouts?

A better way to measure the effectiveness of your workout is to simply execute on a progressive-overload based program. I promise you, you are going to see more results from a consistent routine of resistance training if you’re on a solid program.

And honestly, most people- in the United States, anyways- probably need to worry less about how many calories they’re burning while moving and just MOVE. We’re too sedentary, and before we overcomplicate it, know that we can simply take exercise for what it’s worth in & of itself- movement, which is just GOOD for you both physically & mentally.

No movement is ever wasted – no matter what your fitness tracker says.

So, my friend, I am really sorry if this post burst your bubble, but rest assured, your smart watch is still useful!

Your watch can still be helpful for overall step count, estimated heart rate, distance covered during a walk/run/hike/swim/etc., an estimate of sleep duration, and obviously, time. Again, most of these measurements are going to be estimates rather than numbers to live and die by, and that’s okay.

What’s important to remember about their energy estimates, however, is that they’re far more inaccurate & essentially unhelpful in the ways that most of us wish it were.

You’re probably better off focusing on following a good workout program, utilizing estimates of your TDEE (total daily energy expenditure), and ensuring that you’re adequately fueling day-to-day.

That’s how we’ll continue #BuildingStrongWomen

• Coach Leah