Daily or overly frequent prolonged fasting can lead to metabolic slowdown and impaired glucose tolerance, undermining long-term health and fat loss goals. Instead, strategic, intermittent fasting with adequate recovery periods is more effective and sustainable for metabolic health.
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Daily 16-day fasting feels productive
until it suddenly stops working. And
that's not really willpower. It's
biology. When you compare 12-hour fasts,
24-hour fasts, 36-hour fasts, 72-hour
fasts, you can actually see where 168
goes wrong and why it eventually slows
down the very metabolism that you're
really trying to speed up. I actually
had a moment years ago where I was doing
168 just about every single day. I felt
really sharp. I actually felt really
light. I mean, all the feelings that you
know of, like it feels really good. And
then one morning, I kind of woke up and
I just felt flat. And it was like the
first day I realized, wait a minute, my
energy was really low. My strength had
dipped. And and I remember thinking
like, how am I eating less and somehow
burning less? Like it feels like my
engine's just not running hot. And that
moment sent me down this scientific
rabbit hole of trying to understand the
frequency of fasting, not just the
duration. And once you understand this
and you see it, you can't really unsee
it because fasting is a lot more
effective and honestly just way more
reliable. It's more dependable. It's
sustainable. You can use it as an
accurate tool. And that's what I do now.
And it's so effective. So, so here's
where we're going with all of this
today. And I want to keep it super clear
and really not get too far in the weeds
of the science. But first, we're going
to look at what fasting actually does to
metabolic rate because there's a sweet
spot where the metabolism increases, but
then there's a point where it actually
noses. And then secondly, we're going to
look at glucose tolerance because the
goal isn't to burn fat for one day. The
goal is to become metabolically flexible
long term so you're not having to fast
every day. Then third, we're going to
put it all together so you know how
often you should fast without really
slowing your metabolic rate and also how
to do it without wrecking glucose
control because that can actually
happen. So, let's go ahead and let's
just jump into section one, which is
going to be all about the metabolism
piece with some cool studies there. And
I want to talk about one study in
particular that was in the British
Journal of Nutrition. And it might be
one of the most misunderstood fasting
papers that's out there. And it's good
that I'm covering it because it was a
big one. They looked at 12-hour fasts,
they looked at 36-hour fasts, and they
looked at 72-hour fasts. Now,
intuitively, you'd think that the longer
you go, the more your metabolism ramps
up because fasting does increase
epinephrine and norepinephrine and
adrenaline. So, things do actually ramp
up as you go into a fast. It's partially
true, but only up to a point because
here's what they found. After 12 hours,
the metabolic rate barely changed. It
was really just kind of neutral. I mean,
there was more fat oxidation for sure,
but metabolic rate wasn't changing. What
they found is that after about like 24
to 36 hours, metabolic rate was
increasing. Your body really starts
ramping up norepinephrine. You get a
major increase in circulating fatty
acids in conjunction with the
adrenaline, which just puts you into
like fat burning mode. You really
upshift into that fat burning gear. Then
after about 72 hours, metabolic rate
doesn't go any higher than the 36-hour
mark. So what's happening is that
short-term fasting increases the
catakolamines. So we got adrenaline,
norepinephrine, and that keeps energy
expenditure from dropping. It actually
protects you. But once you extend the
fast beyond 36 hours, but this also ties
in with fasting too frequently, the body
recognizes a consistency pattern. And it
starts to say, "Oh, oh, oh, we're
starving. We should conserve energy." So
what this is telling us is that a
well-timed long fast speeds your
metabolism up. But doing it too often,
even with shorter fasts, or stacking
calorie restriction on top of it on the
days you're not fasting, will slow it
down. So, that brings me to the second
point in this video because short-term
fasting is just one side of the coin.
Uh, we need to kind of talk about how
this all plays together, right? Because
the other side is what happens when
you're chronically undereating without
realizing it. Been my problem for like a
half a decade, right? you get hooked on
feeling good with the lower calories.
And there's a really good study that was
in the American Journal of Clinical
Nutrition, and it looked at what
happened when people overeat for one
week, but then went into a 50% caloric
deficit for 3 weeks, then reed for two.
So overeat one week, then caloric
deficit for 3 weeks, and then refeed for
two. 3 weeks of what most people would
consider just dieting a little too hard.
All right. So, in that short window,
their resting metabolic rate tanked by
266 calories per day. In 3 weeks, their
daily metabolic rate went down 266
calories per day. Almost half of that
was adaptive thermogenesis, meaning that
the body voluntarily slowed itself down
to survive. They lost 5% of their muscle
mass in 3 weeks, which further dropped
their metabolism. So, in other words, if
your fasting routine turns into chronic
calorie restriction, especially with
something like daily 168, you can
unintentionally shut the system down
that you're trying to speed up. And this
is exactly why people feel great for the
first couple weeks of fasting and then
they stall or even a couple of months or
even it just becomes a lifestyle and
just nothing happens. They don't really
change it. They just feel good, but
their body doesn't change. It's wild how
fasting can happen, especially if you
don't have a whole lot of fat on you,
right? So within about 2 to 3 weeks of
continuous reduction in calories, your
metabolism begins to downshift. It's not
months, it's not years, it's 14 to 21
days. Here's the kicker. That same
slowdown does not happen with
infrequent, strategically placed
moderate length to longer fasts. Why?
Well, because the body interprets those
as acute temporary stressors, not
starvation. You also want your body to
be able to recover and build off of
those fasts. What I mean by that is you
have all kinds of cellular changes and
repair that happen during a fast. You
have reorganization, reallocation and
autophagy and then you need to actually
rebuild. It takes protein. It takes
calories to rebuild. So all the mphagy
you're going through where the
mitochondria are going through their own
respective autophagy to consolidate and
get stronger, if you don't have periods
of rebuilding,
that doesn't do you any good. So fasting
is a stressor on the mitochondria.
Calorie restriction is a stressor on the
mitochondria. Then you need to be able
to repair from that stressor. The
stressor is the signal and then you need
the repair. So you don't just
consolidate your mitochondria or
consolidate cells and then continue to
fast and have that happily continue. You
consolidate and then you power them up.
Right? So it's like you want to take all
the junked vehicles in your junkyard,
consolidate all the parts to make one
supercar, but then you got to put fuel
in that supercar, otherwise it's still
just eh sitting there, right? This is
where that product timeline can come
into play. I think this is cool science
with this because this is a compound
uriththnan A that induces mitochondrial
autophagy mphagy. It's been published in
a lot of papers been published in JAMMA
all kinds of different research journals
because it induces autophagy or of the
mitochondria. It's called mphagy. So you
take that regularly but you can take
that even when you're not fasting and it
kind of continues that autophagy effect
and it helps rebuild those mitochondria.
So, this is one of the most foundational
like longevity compounds that's out
there, but personally, I take it more so
because I get better recovery and I feel
like my mitochondria is stronger from
it. I popped the link down below. That's
a special discount link, so you can use
that link down below so you can use
their capsules. They've got a powder.
They also have gummies, which taste
pretty good, too, and they don't have
sugar in them. So, that link is down
below. These guys are great. They're a
Swiss company that really focuses on
precision, too. So, this stuff is legit.
Link down below. So, don't crash your
metabolism. All right, we've talked
about that. And now that we've covered
that piece, let's jump into part two of
this, which is the glucose tolerance
piece, cuz fat loss is not just about
what you're burning today. It's about
what your body is choosing to burn today
and tomorrow. Okay, the rate limiting
step here is how well your cells respond
to insulin. And you probably know this
by now. Fasting helps with insulin
dynamics and all this, but if your
glucose tolerance is dropping, your
insulin goes up and your fat burning
shuts off. And that's not good, right?
That could be a serious problem. And
there's a really interesting study that
was in the Journal of Applied Physiology
that kind of outlined this a little bit
more. They had subjects fast for either
13 hours or 72 hours before actually
eating a test meal. And after the
72-hour fast, fat oxidation was higher,
as you'd expect. But glucose tolerance
got worse. Their blood sugar glucose
spiked higher, insulin spiked higher,
and glucose oxidation dropped. And this
is the body going, I've been running on
fat for a few days. I'm not switching
gears very easily over here. Like the
body likes to kind of find these
grooves. So researchers think that this
might be due to elevated growth hormone
levels, which is good, but it also could
be elevated free fatty acids that are
impairing the insulin signaling. Again,
it has its place, but may not always be
a good thing. So long fasts burn fat
like crazy, but if you do them too
often, you start losing your ability to
process carbs normally. And you might be
thinking like, I'm not going to have
carbs anymore, so who cares? There will
come a time when you have carbs. So,
let's be real here. I don't care. Even
the strongest carnivore people still
occasionally will have carbs. It just
happens, right? And are you 99% of the
population or you 1% of the population?
Who's going to eat carbs? Right? So,
even me, I don't eat a lot of carbs, but
I want my body to be adjusted to them.
But here's the cool counterpoint because
there was a study that was in
endocrinology and this was a mouse study
but they found that mice doing three
24-hour fasts per week uh like
non-consecutive. They did this and the
glucose tolerance improved dramatically
if they were doing like these 24-hour
fasts non-consecutive glucose tolerance
improved. They got better. So again,
frequency is everything. How often we do
them, how long we do them. Shorter fasts
done intermittently with breaks improve
insulin sensitivity because you have a
period of time in between to actually
mess around with your new insulin
sensitivity that you just got from
fasting. Ultra long fasts done too
frequently actually impair it. I think
this is where like Peter Ao was like
what he was getting at when he was
talking about how he quit fasting. Like
I think he was just like an all or
nothing guy and going like full boore
into fasting and was doing like long
fasts all the time. Of course that's
going to be problematic. like no one's
saying to do that. Anyway, now that
we've covered the metabolic rate and
glucose tolerance piece, I want to move
into the part where we kind of tie it
all together. How often you should
actually fast, like what you can do
personally. And here's the pattern that
the research paints uh when you kind of
overlay everything we've talked about.
If you fast every day, especially with
168, and you unintentionally undereat,
you have about 2 to 3 weeks of a window
before your metabolism begins to slow
down. And that's why people see amazing
results for like two, three weeks and
then the wheels fall off. But when you
back up and you kind of zoom out, the
research says something pretty
empowering. You don't need to fast every
day to get the benefits. Okay? You might
not get as strong of fat loss benefits
right in the beginning, but you're going
to get them for ever. In fact, not
fasting every day is what keeps your
metabolism high. If you do one 36-hour
fast per week or two non-consecutive
24-hour fasts or even three separate
16-hour fasts, you get the
norepinephrine bump. You increase fat
oxidation. You improve glucose
tolerance. You avoid this metabolic
downshift. Here's the part I really want
people to hear. Consistency doesn't mean
every day. We have it programmed that we
need to grind every day. Like,
consistency just means it's repeatable.
It means it's sustainable. It means it's
something your body can adapt to long
term without defending itself. The Cell
Reports Journal data is actually
fascinating here. They found the longer
that you can sustain a form of caloric
restriction across your life, fasting,
etc., not extreme restriction, just mild
restriction, the longer you can sustain
it, the more you will see improvements
consistently and reliably. You're going
to see improvements in cellular
housekeeping, in autophagy, in metabolic
health markers, in fat loss, but you can
only sustain it long term if you're not
constantly shrinking your metabolic
rate. Fasting works because it is a
pulse. It is a stressor. It is a
strategic interruption. Okay? When it
becomes daily deprivation, the system
breaks down. So, here's what I would
suggest. Okay? Based on everything we've
covered today, use fasting like a
sprint, not a marathon. Intervals, okay?
Go hard for a short burst and take a
break. If you're doing daily 168, you
got to give yourself a reset every
couple weeks. Okay? I understand it's a
lifestyle thing and it works great. You
have to take a few days off every couple
weeks. Then if you prefer longer fasts,
use them sparingly. Do them once a week,
maybe once every other week, okay? It's
enough to get the metabolic pop, but not
enough to really trigger the slowdown if
you're keeping an eye on it. And also
keep the protein super high because
you're breaking down. you need to
rebuild. Don't be afraid of mTor. Don't
be afraid of rebuilding. Okay. Let me
give you three simple takeaways you can
implement just right now. Okay. Number
one, if you are doing daily fasting,
insert a break every 7 to 14 days for
like 2 to 3 days. Okay. Let your
metabolism breathe. Just let it breathe.
Number two, if you like longer fasts,
try doing one or two 24-hour fasts
weekly or at least like maybe one
36-hour fast every 10 days or every two
weeks. Do not do multiple days in a row.
Is never a real reason to do that unless
you have a very specific thing. Number
three, keep protein high during eating
windows to preserve muscle. Okay, this
is super important because protein is
your absolute like metabolic insurance
policy. It's making sure you have that
muscle so that you can have the
metabolism going forward. And number
four, pay attention to how you feel day
to day and week to week. If your energy
is dropping, that means your calories
are probably too low the following
couple of days or the previous couple of
days. So, if energy drops, if strength
drops, or if sleep falls off, if it
feels really weird, you're not sleeping
well, that is your really early warning
sign that you're sliding into metabolic
conservation. At the end of the day,
it's not about discipline. It's about
sustainability, rhythm, and consistency.
When you hit the right rhythm, your
metabolism doesn't fight you anymore. It
works with you because that's the way
it's supposed to be. It's a beautiful
system that we have from our creator,
right? like we can work in harmony with
our environment and that includes our
food and that matters because fasting is
often used for one specific reason,
right? It's to drive autophagy and
cellular repair and all these other
things like to clean up and that's
important because fasting is used for
all kinds of reasons like whether it's
spiritual, whether it's cellular cleanup
or fat loss or just because it feels
natural, right? I think there's some
other components of fasting that people
really like that can activate some of
these sort of longevity like cleanup
attributes. In another video, I broke
down a compound that's derived from an
actual leaf, believe it or not, that
activates many of those same repair
pathways without requiring a lot of
extended fasts. Or you could couple it
with some fasting to get an extra
benefit. It just gives you another tool
when it comes down to cellular repair on
the days maybe when fasting isn't the
right tool or when you want to like
accelerate a fast a bit more. So, that
video is right here. I recommend you
check it out. Please do subscribe and I
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