Alright, time to get in shape.
Ready watch!
*beep* *beep*
You ran 1.3 miles and burned 300 calories.
WOW!
Here we go again!
*panting* T: That’s gotta be twice as far than yesterday!
You ran 1.2 miles and burned 205 calories What?
That doesn’t make any sense!
Okay here we go- *beep* You ran 18.4 miles and burned… negative
204 calories YOU STUPID PIECE OF-
Today, we’re going to talk about a little fitness device that’s been all the rage
in recent years, thanks in no small part to the heavy advertising of smartwatches being
a reliable fitness tracker.
And tracking one of the fitness metrics that has eluded consumer capabilities until now
is arguably its most appealing feature and that is of course tracking your calories burned.
But have you wondered exactly how these little gadgets work?
The concept that a simple wristwatch can do so much can be quite mindboggling when you
consider that research-grade methods of tracking calories involves equipping a CO2 respirator
or confining people in melancholic metabolic chambers that measure every breath you take,
every move you make.
And, even then they are subject to some degrees of error.
Obviously, a wristwatch doesn’t measure the same things as a mask or a chamber, so
it requires something else completely.
And one of which comes from that flashy green light on the underside of your watch.
We won’t get into too much detail as to how it works, but by emitting green light,
the watch’s optical PPG sensor tracks blood circulation of your wrist, which outputs data
to measure a little thing called your heart rate.
Using your heart rate, along with your age, height and weight, we can determine a close
estimate of one’s VO2, or oxygen consumption, which itself can be used as an estimate in
calculating calorie expenditure.
Now the use of heart rate and VO2 to calculate calorie estimates is nothing new, but the
keyword here is estimates, and a loose one at that.
And it’s assuming that the heart rate monitor in your watch is accurate as well, which in
one case study has shown that heart rate measurements can vary greatly simply by adjusting the tightness
of the wristband.
So you have an equation that is only a loose estimate of calorie expenditure and you also
have a variable in that equation, heart rate, that might not be accurately measured.
Not the best look so far.
However, smartwatch manufacturers stated that their data collection involves more than just
heart rate and user information.
Some boast a complex, secret proprietary software and recently, some equipped with accelerometers
even claim to measure every single movement you make, all conveniently through a device
that can also read your notifications.
This lack of software disclosure, however, creates a barrier for researchers to understand
how the devices work.
We don’t know exactly what’s being measured or whether the formula they’re using is
reliable.
All we’re really getting are the companies’ word.
Now, overall, there’s nothing exactly wrong with getting an estimate if the estimate itself
is not far off from the actual numbers.
Even the nutrition information on food packaging are estimates, which can vary based on how
the food is processed.
But for food labels, they’re widely considered as reliable enough thanks to rigorous, disclosed
testing.
For fitness trackers, though, can we say the same thing?
Are they good enough?
Again, what we already know, the variability of heart rate data, an undoubtedly huge part
of the equation no matter what fancy proprietary software the watch might have, can itself
lead to significant differences in estimates.
Just knowing that should already be reasonable enough to doubt its reliability.
But let’s look a bit further in the studies.
A 2017 study tested multiple smartwatches available from companies like Garmin, Fitbit,
and Apple.
What they found was pretty interesting.
Along with calories, they also compared data for steps and distance traveled between the
devices.
What they noticed was that none of the devices were ever in agreement for any measured outcome,
with the Apple Watch reporting as much as 20% more steps and 40% more distance traveled
compared to the other watches.
In terms of calories, at times there was as much as a 35% difference in calories measured
between an Apple Watch and Fitbit Flex.
So just comparing one device to another, there can be very different readouts, which no doubt
again makes you wonder exactly how accurate they are.
But the big test is comparing these fitness watches to tried and true gold standard measurements
tools.
In 2019, researchers set out to do just that.
In this study, researchers pit five different fitness watches against a metabolic calorimetry
chamber, and measured estimated physical activity calorie expenditure.
Compared to the chamber, four of the five watches reported fewer calories burned, with
one reporting roughly 500 physical activity calories fewer than the metabolic chamber.
The remaining watch overreported by roughly 110 calories.
And although using a metabolic ward is great in terms of testing accuracy, we obviously
don’t live in huge gas-measuring boxes so the researchers also performed a 15-day free
living trial.
The watches were compared to another research-grade tool called doubly-labeled water, a special
type of water that, when administered, can measure a subject’s daily metabolic rate
during free-living conditions.
In this trial, we also see similar under reporting across the devices, this time in all five
of them with the greatest offender underreporting by about 700 calories per day.
Those are some pretty huge discrepancies, needless to say.
Now in fairness, this study was in 2019 and it is likely that manufacturers made some
improvements to their top secret software since then.
Although another 2022 study did find under reporting issues as well, notably in underreporting
heart rate.
(Jagim, 2022) And the 2019 study didn’t include one of
the more popular watches, the Apple Watch.
Whether Apple or anyone else has the technology to surpass the competition, however, remains
to be seen.
But that’s what we see in the research so far.
And based on what we know, are smartwatches and other similar devices accurate calorie
estimators?
Probably not, but it is interesting that most of the data suggest an under-reporting of
activity and calories rather than over-reporting.
I personally thought it would be the opposite.
This might have to do with the limited ability of tracking specific exercises, especially
intense exercises that don’t require much arm movement, like cycling, or exercise that
don’t require much distance traveled, like lifting weights.
Whatever the case, it’s clear that in terms of specifically tracking calories, the tech
isn’t there just yet.
It will still largely boil down to you figuring out not how many calories you’re burning,
but rather how much you’re eating that will play the ultimate role in your weight changing
goals.
Still, what’s great about fitness watches is that it is consistent in tracking trends
and changes.
Even though the numbers aren’t entirely accurate, if the watch can detect an upward
trend in calories burned by you increasing exercise, then that’s still useful data.
It might even mean quite a lot if seeing these trends inspire you to maintain a more active
and healthy lifestyle.
In fact, a 2022 survey in the IKSAD journal found that only 20% of respondents were exercising
for more than 4 days a week before wearing a fitness watch but that number went up to
34% after.
Another limited review further discovered that sedentary individuals were more likely
to increase physical activity when using a wearable fitness tracker.
(Nuss, 2020) And even in terms of health, in one case study,
a smartwatch detected an irregular change in a woman’s resting heart rate, which lead
to her getting diagnosed and treated for a serious inflammation condition of her blood
vessels.
(Gkikopoulos, 2022) These other health and fitness impacts can
be extremely useful to the point that I would definitely suggest if you can get a fitness
watch, then you should.
Just understand its pros and cons and try to not to adjust it too often when you’re
wearing it to not throw off the sensor too much.
I’ve personally been wearing one for the past three years.
Apparently, burned about 85 calories since then!
Awesome!
But that’s what we know about smartwatches and calorie tracking so far.
Not great but not entirely junk and still great for many other cool fitness stuffs.
If you already have one, keep using it, and if you’re thinking about getting one, it
gets a thumbs up in my book.
*beep beep* Oh, burned about 5,021 calories while recording
this video.
Sounds about right.
If you enjoyed this video, please give it a smarty thumbs up and share it with your
watch loving friends.
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As always, thank you for watching and GET YOUR CALORIMETRIC PROTEIN!