The Truth About Fasting: Beyond the Hype

Fasting has become a health buzzword, but beneath the hype lies a complex metabolic tool with specific benefits and important caveats. In this comprehensive exploration, I break down the science behind different fasting approaches and reveal why not all fasting styles deliver the same results.

The episode distinguishes between four major fasting types that are often confused: prolonged fasting (multi-day), intermittent fasting (alternate day or 5:2), time-restricted eating (daily eating windows), and fasting-mimicking diets (low-calorie regimens). Each approach affects your body differently, and understanding these distinctions is crucial before embarking on any fasting regimen.

While fasting shows impressive benefits for weight management, metabolic health, inflammation reduction, and potentially even cancer treatment support, these advantages come with important qualifications. The podcast reveals a critical insight often overlooked: fasting paired with poor nutrition during eating windows can negate most benefits and potentially cause harm. For those primarily interested in weight loss, the evidence suggests early time-restricted eating (finishing dinner by 5-6pm) provides the most sustainable approach with the strongest scientific backing.

The episode also addresses special considerations for athletes, medication users, and those with specific health conditions. We explore why some people might experience rising cholesterol with certain fasting approaches, how fasting affects muscle maintenance, and the emerging research on fasting's role in cancer therapy.

Whether you're curious about skipping breakfast, considering a five-day fast, or simply want to understand how your eating pattern affects your health, this evidence-based breakdown cuts through the confusion to help you make informed decisions about incorporating fasting into your lifestyle. Subscribe now for more science-backed insights on optimizing your health through evidence-based nutrition and lifestyle medicine.

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Episode Transcript

Speaker 1 (00:11):
Hey everyone, welcome to Season 2 of the Dr Jules
Plant-Based Podcast, where wediscuss everything from
plant-based nutrition to themain pillars of lifestyle
medicine medicine.
Yo, plant-based buddies,welcome back to another episode
of the podcast.
Today we're going to be talkingabout the science of fasting.

(00:33):
Part one will be the what, thewhy and the how to fast, and
part two will be about longevity, cancer, inflammation and
possible risks that could comewith fasting.
Now, fasting is very popular.

(00:58):
Some people think it's thefountain of youth, and a lot of
hyperbolic claims surroundfasting.
But the most important thing isthat there's a lot of nuance to
consider.
There are potential risks withfasting, so if you're going to
do it, you want to make sure todo it the right way.
So in this two-part series,we'll unpack everything you need
to know about fasting Not thetrends, but the science behind

(01:20):
it, Whether you're curious aboutskipping breakfast or
considering a five-day fast thisis for you.
Now let's start with a simpletruth Fasting is not

(01:41):
biologically extreme.
Now it may be socially extreme,but we've evolved to go through
cycles of feast and famine.
In fact, our metabolism isbuilt to be able to switch
between storing energy andburning it.
This ability is calledmetabolic flexibility.
What I would consider to beextreme is eating every two

(02:02):
hours.
That's a more modern invention.
Now fasting is an umbrella termand there are several different
evidence-based types of fasting.
So let's talk about the majorones First.
We have to differentiateprolonged fasting from
intermittent fasting, fromtime-restricted eating to

(02:26):
fasting-mimicking diets.
So when someone is talkingabout fasting, these four
different types are alldifferent types of fasting
regimens and they all havedifferent benefits and different
risks.
So if we start with prolongedor extended fasting, typically

(02:47):
this could include not havingany calories for more than 24
hours, but it's typicallyreserved for longer fasts that
are multi-day.
Intermittent fasting oftenrefers to alternate day fasting,
where you eat one day and fastanother.
Or some people even useintermittent fasting to describe

(03:10):
the 5-2 model, meaning that youwould eat for five days and
then fast for two.
The term intermittent fasting isoften confused with
time-restricted eating or tiare,and that simply refers to
eating within a specific dailywindow, like, for example, you

(03:31):
eat only from 10 am to6 pm andthen, in terms of tiare, we have
early tiare or we have latetiRE.
Early TRE would simply meanthat your eating window is
earlier in the day.
For example, you stop eating at4 pm and late TRE late

(03:55):
time-restricted eating couldrefer to skipping breakfast and
eating from noon to 8 pm, forexample.
Noon to 8pm, for example.
We also have fasting mimickingdiets or FMDs.
These are diets that are verylow in calorie and that mimic
fasting biology and are used forcancer treatment, weight loss

(04:18):
and to lower inflammation.
Each of these different typesof fasting regimens have
different effects, differentpros and cons, so let's break
them down one by one.
Now, across the board andacross all fasting regimens,

(04:39):
studies show reduced body weight, improved growth hormones,
improved autophagy, improvedglucose tolerance, better
insulin sensitivity, lower bloodpressure, lower cholesterol,
lower fatty liver, improved gutfunction, improved inflammatory
markers and even better improvedmetabolic health, independent

(05:03):
of weight loss.
But not all fasting styles areequally sustainable or equally
beneficial.
Intermittent fasting, whichoften refers to alternate day
fasting, or 5-2 methods, oftenshow weight loss.
But let's be clear if caloriesare the same, this type of

(05:25):
fasting does not lead to moreweight loss than calorie
restriction.
For some people, intermittentfasting is simply a more
convenient way of cuttingcalories, and if you want to
lose weight, you either cut outcalories or cut out hours of the

(05:47):
day where you're eating them,or some people will cut out
specific food groups.
Now, alternate daily fastingmay be better for preserving
muscle mass and bone mass, butstudies also report increased
LDL cholesterol, sometimes by upto 10%.

(06:07):
So this needs to be consideredif you're already at higher
cardiovascular risk.
And compliance is also lowerwhen we compare alternate daily
fasting to time-restrictedeating.
So it may have benefits interms of weight loss, but not
more than the equivalent incalorie restriction, and it may

(06:31):
even come with some risks ofincreasing LDL, but may be
better for preserving musclemass and lean mass.
Now, TRE, or time-restrictedeating, is probably the star of
the show, and TRE limits whenyou eat, not what you eat and
not how much you eat.

(06:52):
It's about eating inside of aeating window, so, for example,
we can have early TRE, whereyour eating window is at the
beginning of the day, or lateTRE, when your eating window is
at the beginning of the day, orlate TRE, when your eating
window is at the end of the day.
The most common windows are12-12, so 12 hours of eating and

(07:13):
12 hours of fasting.
Some windows are 14-10 and someare 16-8.
And the early TRE, where theeating window ends before 5pm,
typically seems more beneficialthan late TRE, and 75% of
studies show that early TREimproves blood glucose control.

(07:37):
Some even suggest that TRE mayreduce blood pressure by
improving sodium excretion.
In circadian biology matters,melatonin reduces insulin
response, so eating late atnight might cause higher blood
sugar from that same meal whencompared to if you would have

(08:01):
eaten it earlier in the day.
So it ends up that fasting issimply an umbrella term and can
refer to a lot of differenteating patterns.
Prolonged fasting is differentfrom intermittent fasting, which
is different fromtime-restricted eating and
fasting-mimicking diets.

(08:21):
They all have differentbenefits, but they also carry
different risks.
Some are more sustainable thanothers.
Carry different risks.
Some are more sustainable thanothers.
Some help with metabolicdisease and weight loss, while
some will increase the risk oflosing muscle mass.
Most people care about fastingbecause they want to lose weight

(08:45):
, but in terms of weight lossthe benefits of fasting don't
seem to be superior to normalcalorie restriction.
Without fasting, an early TRE,when your eating window ends
before 5pm, is more in line withyour circadian rhythms and

(09:10):
seems to have the best metabolicbenefits.
Now what you need to consider ifyou are fasting for more than
just weight loss, is the qualityof your diet during your eating
window.
Now, yes, you will lose weightand there will be benefit

(09:31):
through weight loss if you areoverweight, but what happens if
your diet is of very poorquality?
The chances that you're goingto hit 18 mg of iron or 1000 mg
of calcium or 400 milligrams ofmagnesium.
If you're eatingultra-processed food during your

(09:54):
eating window, the odds of allof these nutrient goals being
met are quite low.
So I see people fasting forweight loss while eating very
poor diets.
Now what happens to thesepatients?
As they put themselves at riskof nutrient deficiencies?

(10:15):
But, most importantly, they'reprobably not eating 1.2 to 1.6
grams of protein per kilogramper day and they're risking
their muscle mass.
So what happens is that thesepeople, they do lose weight, but
they lose muscle, and withmuscle loss comes a decline in
your BMR, your basal metabolicrate.

(10:38):
It will cost less energy toexist as a smaller person.
So when you start eating again,if you have not changed your
eating habits or your lifestyle,your basal metabolic rate will
be lower and you'll just gainthe weight right back.
So just be mindful that ifyou're fasting for anything else

(11:01):
than inflammation and longevityand cancer risk and you're
fasting specifically for weightloss, make sure that your diet
is dialed in, because if not,you may actually blunt any
benefits that come withlongevity and cancer and
inflammation if you're eating acrap diet.

(11:21):
Now one could argue what wouldbe the benefits of fasting if
you're going to undo all ofthese benefits by eating a
pro-inflammatory diet that'sdeficient in fiber and increases
cancer risk?
So that's exactly what we'regoing to be diving deeper into
in part two so some peoplearen't just fasting for weight

(11:49):
loss.
Some people are fasting forinflammation, for longevity, to
reduce cancer risks, and in parttwo we'll talk about all of
these things, including some ofthe risks that we need to be
aware of.
So for all of you who are usingfasting for its
anti-inflammatory benefits, Ican reassure you.

(12:12):
Fasting does lower inflammationthrough multiple mechanisms.
Growth hormone will surge notjust during deep sleep but also
during fasting, and thisstimulates repair.
Time restricted eating has beenshown to lower ghrelin levels,
which is the appetitestimulating hormone.

(12:34):
It also decreases inflammatorymarkers like CRP and IL-6.
And in fasting, hunger doesn'talways increase, especially with
time-restricted eating.
The body adapts, so people whofast more often find it

(12:55):
progressively more easy tosustain.
Now for those of you who fastfor longevity, we do have rodent
studies showing that even a 10%calorie restriction can extend
lifespan, and that's probablybecause of a process called
autophagy.

(13:15):
Now, autophagy is our cellularcleanup system and it's enhanced
by fasting, by exercising andby restricting calories.
So fasting isn't magic, it'sjust a way to make calorie
restriction easier for somepeople.
We even have insights fromstudies like meta-analyses that

(13:39):
have looked at this, and theincrease in autophagy seen
during intermittent fasting isabout the same as during the
equivalent calorie restriction,so fasting is a tool that makes

(14:00):
calorie restriction more easyfor some people, but not this
magical entity that magicallyincreases autophagy.
Now I've also had patients askme about fasting and cancer.
Now this area is still emerging.
It's not well studied, but itis promising.
We know that fasting reducesinsulin, glucose and IGF-1, all

(14:24):
of which are associated withcancer growth.
Dr Walter Longo has publishedon fasting and cancer and he has
a theory called differentialstress resistance theory that
proposes that fasting willprotect healthy cells while
making cancer cells morevulnerable to chemotherapy.

(14:44):
But again, we need to becareful because prolonged
fasting or full fasting canincrease the risk of cachexia or
dangerous weight loss.
That is often seen when you'rebattling cancer and that's why,
in clinical trials,fasting-mimicking diets are
preferred.
Typically, these patients willgo on very low-calorie diets

(15:08):
that mimic fasting and stay onthem for about five days and
then go back to a normal dietfor about a month.
The studies we have on thesetypes of diets do show benefits
in terms of increasingresponsiveness to chemotherapy.
It's important to never fastaround chemo without clinical

(15:32):
supervision.
We know that cancer patientsare typically losing weight,
losing muscle mass.
They have trouble eating, soit's very important to talk to
your oncologist and to befollowed by a registered.
Now it's important to considerthat there are many risks and

(15:58):
red flags when it comes tofasting.
Fasting is a stressor.
Now that can be good in theright dose.
Don't overdo it Because if youdo, you risk electrolyte
imbalance, brain fog, moodchanges, refeedinging syndrome,

(16:20):
muscle and bone loss.
I had a patient who went on aon a prolonged fast and took
diuretic medication for herblood pressure and had
life-threatening hypokalemia,which is a condition that's
described as very low potassiuminside of your blood and that
means you have very lowpotassium inside of your cells

(16:43):
and that could cause, like heartrhythm disturbance and muscle
weakness and cramping andneurological symptoms that can
threaten your life.
So if you take blood pressuremeds or glucose lowering
medication or have a history ofeating disorders, please fast

(17:05):
under medical guidance.
Now, out there online you canfind a lot of confusing
information, but out here in thereal world, there are certain
fasting regimens that work best.
Now I use fasting in my life andso I need to keep it practical.

(17:26):
It needs to fit my busyschedule, needs to fit my goals
and it cannot negatively impactathletic performance.
So here's what I recommend,based on the evidence, but
recognize that these fastingregimens may not fit your needs.
Now, if you're going toconsider fasting, I would

(17:49):
suggest consider early,time-restricted eating.
It's simple.
It just means finish eating by5 or 6 pm and try not to eat
after supper.
This basically aligns yourfeeding or your eating with your
circadian rhythm, and we knowthat circadian aligned eating

(18:09):
will improve blood sugar control, blood pressure and fat
metabolism.
Now other people would benefitfrom FMD or fasting mimicking
diets.
This is basically a pattern offive-day cycles, monthly or
quarterly, especially in thoselooking to improve metabolic
health.
You go on very low-caloriediets that are low in protein,

(18:42):
are low in protein, thatprioritize plant protein and
nutrient-dense plants.
You eat this way for five daysand then, a few months later, or
a few times a year, you repeatthat cycle.
Regardless of the fastingregimens that you choose, always
consider front-loading yourcalories, and you may have heard
this before eat breakfast likea king, lunch like a prince and

(19:06):
dinner like a pauper.
Now, final words, you don'tneed to fast perfectly, you just
need to do what works for yourbody and your life.
Fasting isn't magic, but it's apowerful metabolic tool when
it's used wisely.
It can improve blood pressure,blood glucose, control,

(19:29):
cholesterol.
It can help simplify calorierestriction.
It can help you lose weight.
It improves autophagy, but notmore than the equivalent
calorie-restricted diet.
So fasting is not magical.
It is a tool.
You can pair it with good sleep, good movement, connection and

(19:51):
plant-based nutrition, becauseyou need to have a healthy diet
inside of that eating window.
If you fast to lose weight andyou do not eat a healthy diet,
you risk metabolic disturbancesand you probably negate any
benefit that you had from thefasting.

(20:11):
And in people that go on crashfasting regimens that are very
severely calorie restricted,they tend to lose muscle mass.
When you lose muscle, yourbasal metabolic rate goes down
because it basically takes lesscalories to exist at rest and

(20:33):
then when you start eating anunhealthy diet again, you regain
the weight and undo all of thehard work you had done.
So fasting is a tool.
I prefer either fasting,mimicking diets or early TRE.

(20:53):
That's the way that isevidence-based to improve
metabolic function, lose weight,increase autophagy, and for me
it's just simply more practical.
It fits in my life and itdoesn't negatively impact my
training, my workouts, my runsor my ninja competitions.

(21:14):
The most important thing is tosimply find a fasting regimen
that works for you.
Cool Right on.
I hope that this has cleared upsome of the confusion behind
fasting.
Remember that fasting is anumbrella term.

(21:35):
There are different fastingregimens, all with their
individual pros and cons.
Some are more sustainable.
Some will fit your needs andyour desires.
Choose the one that's right foryou.
But if you decide to embark ona fasting journey, make sure to
talk to a healthcare providerabout it, because there are

(21:57):
legit risks that come withfasting Right on.
Thanks so much for tuning in.
I hope you've learned a lot.
We'll see you in the nextepisode, peace.
Hey, everyone, go check out mywebsite plantbaseddrjulescom to

(22:27):
find free downloadable resources, and remember that you can find
me on Facebook and Instagram atDr Jules Cormier, and on
YouTube at Plant Based Dr Jules.