Today we are once again gonna give an update on a very popular fitness trend thanks to
some newly published research.
And of course if you’re big fan of new science and data like myself, then stick around and
learn a bit more about this topic.
And that topic, is fasted cardio!
Hi, for those of you that don’t know me, I am PictureFit and I like making health and
fitness videos using good ol science and data.
I also like hamburgers.
Thought you’d wanna know that just in case.
The beautiful thing about science is that there’s always new information coming out
that allows us to shape the way we approach the world and allow us to take data out of
context to win arguments on the internet.
And, sometimes we just make things up.
Hey, it helps us sell basic recipe books and supplements, so why not?
Fasted cardio is kind of somewhere in the middle, a bit of truth, and a bit of ehhh,
not so fast.
Let me explain.
In terms of things being truthful, the primary mechanism touted by fasted cardio lovers,
namely an increase in fat oxidation, does in fact occur.
In other words, if you’re trying to burn fat, fasted exercise might be great because
it does rely on more fat burning for energy during exercise and slightly after.
Eating a meal before your cardio, on the other hand, ends up restricting fat oxidation, which
means your body burns more carbohydrates for energy instead.
And if you immediately stop ALL of your bodily functions at that very moment you stop exercising,
or in more depressing terms, you DIE, then sure, fasted cardio wins out on the matter
of burning more fat.
Unfortunately for those of you still alive, as your day continues, research has shown
that, hours after exercise, participants that performed fasted cardio shifted to burning
more carbohydrates and less fat for energy whereas the opposite is true for those that
did fed cardio.
So, all you’re doing is flipping the script for a short amount of time but that quickly
reverses as the day goes on.
Gosh darn body, you and your silly homeostasis.
But as great as mechanisms might be, what matters most is the actual results we see
in research.
Before we jump into the new research, let’s first look at the research we already have.
In 2014, a study compared healthy young female participants after 4 weeks of doing either
cardio fasted or after consuming a 250-calorie shake.
The cool thing about this study is that both groups had a nutrition plan meant to induce
a 500-calorie deficit, which did lead to both groups losing weight and fat.
If fasted cardio indeed have any extra metabolic and fat-burning advantages, then we would
see greater losses.
But, we didn’t.
There were no significant differences between the two groups in terms of weight and fat
loss.
So, fasted cardio, what’s up with that?
In fairness, it was a pretty short study with only 20 subjects, so not the biggest sample
size.
But of course, there’s MORE!
And not just more, but the morest of them all, a systematic review and meta-analysis,
which is a type of study that evaluates data from multiple studies and data points for
a given outcome to draw a more complete conclusion.
Basically, it’s taking all the information we have on something so we can see the bigger
picture.
Kind of like getting a D- in Biology 101 even though you got a B+ on the final but then
you failed the midterms, did none of the lab homework, and was busy sniffing the gooey
stuff used for the ECG machines.
True story.
In this 2017 meta-analysis, after reviewing the 5 relevant studies on the matter, the
researchers concluded that neither fasted nor fed cardio invoked any meaningful changes
to weight and body composition.
Instead, the biggest factor, if you’re trying to lose weight, is, wait for it, “creating
a meaningful caloric deficit over a period of time.”
Dun dun dun, calorie deficit.
Harder to get away from than your leg days!
But in fairness again, although this is more data, it’s still only five studies with
a total of 96 subjects.
That’s an average of just 19 participants per study.
Still, the findings were consistent across the data.
That is, the effects of fasted and fed cardio, in the grand scheme of things, were not all
too significant nor different.
And to top things off before the new research, we have a 2018 meta-analysis that investigates
another important factor to consider, and that is exercise performance.
What the researchers in this case found was, by eating a meal before exercise, performance
was better if the exercise lasted for more than 60 minutes.
Do note though, that the observed benefits were only when meals were consumed 3 to 4
hours prior to exercise, and performance seems to be the same for exercises lasting less
than 60 minutes.
But, that’s another strike on fasted cardio.
At most, it provides zero benefit to performance, and at worst, fasted cardio might actually
be detrimental, which is… not too surprising.
And now, let’s finally dig in to the latest research published in late 2021.
Let’s first preface this with three key questions to ask about the worthiness of fasted
cardio: The first two is, does fasted cardio provide
a body composition benefit?
AKA, does it help us burn more fat overall.
And, does it provide a performance benefit?
As we’ve seen so far, the answer is NO to both.
But the third question we haven’t touched on is, does fasted cardio provide a calorie
benefit?
We know that a calorie deficit is what helps us lose weight and fat in the first place,
yes.
But what if fasted cardio can actually make it easier for us to achieve that calorie deficit?
And that’s the question we might have an answer to with this new study, which is a
meta-analysis as well.
Awesome.
The researchers investigated the impacts of fasted exercise on the matter of, as we alluded
to, energy intake, or calories consumed, and energy expenditure, the calories burned.
And they did this in a very cool way of breaking down the participants into four different
categories.
One, subjects performing fasted cardio and then had a meal afterwards.
Two, subjects performing fasted cardio without having a meal afterwards.
Three, subjects performing fed cardio and then had a second meal afterwards.
And four, subjects performing fed cardio without having a meal afterwards.
And what they found was very interesting.
Subjects that performed fasted cardio and did not have a meal right after ended up consuming
significantly fewer calories in a 24-hour period.
And it wasn’t a small number neither.
It was FIVE HUNDRED calories fewer on average than participants that performed fed cardio
without a meal after.
However, the same group of fasted cardio with no meal also ended up burning fewer calories
overall, equating to about .16 calories less per minute, or about 10 calories per hour,
which amounts to 240 calories fewer per day.
Not as significant of a drop in calories burned compared to calories consumed, but it’s
still very important to point this out.
Of course, there are caveats here.
Even though this is a meta-analysis, the amount of studies that directly looked into the effects
of 24-hour energy consumption in a group performing fasted cardio with no meal was only 2 out
of 23 studies analyzed.
And perhaps the most important finding in terms of a sustainability perspective, is
that the fasted cardio with no meal group had by far the highest subjective hunger ratings
out of all groups.
They were undoubtedly hungrier throughout the day, which can lead to adherence issues
down the line.
So yes, there are indeed positives in the data but with very important strings attached.
But Mr. PictureFAT, the fasted cardio group still ate fewer calories!
Yes that’s true, but in my opinion, the results only lead to asking a whole ‘notha
question.
When exactly is fasted cardio still fasted cardio and not just simply… fasting?
Cause if we’re saying that in order to reap the benefits of fasted cardio, we need to
not only skip your meal before cardio, but also the meal after… then the cardio part
doesn’t really have much to do with it.
You’re just simply narrowing the window of time in which you can eat.
And in that case, we do know fasting protocols like intermittent fasting, which narrows the
eating window, can help people lose weight and fat by making it harder to overeat.
Whether you decide to do cardio during your fasting window or not, seems rather irrelevant.
So, with that point, let’s finally circle back to the third question: does fasted cardio
itself provide a calorie benefit?
When thinking of fasted cardio in the more traditional sense of not having a meal before
exercise but instead after, then in my opinion, the answer is no.
And, that is supported in this new study: In the fasted cardio group that did eat a
meal after, they did not have a significant drop in 24-hour energy intake nor burn more
calories, and worse yet, they still had slightly higher subjective hunger ratings.
Take that for what you will.
With the answers we now have, let’s ask the ultimate questio23
Studies totaln: should you still do fasted cardio?
Well, the answer is honestly, it depends.
But only it depends on if you like it.
If you feel like YOU perform better with fasted cardio or you just have some sense of joy
in doing it, then hats of to ya.
It’s better than doing no cardio at all.
Just don’t be one of those that get lost in the weight loss sauce of overhyping it.
Otherwise, I have some recipe books and supplemetns to sell ya.
If you enjoyed this video, please give it a fasted thumbs up and share it with your
cardio-loving friends.
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As always, thank you for watching and don’t forget to GET YOUR PROTEIN!