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Intermittent Fasting Explained: How It Helps Weight Loss | Nutritionist Explains... | Myprotein
Jan 30, 2025
Intermittent Fasting has been a popular diet trend in the last 10 years. An expert nutritionist, explains what it is and how it works.
What is intermittent fasting? There are a few different types but at its heart, intermittent fasting is an eating pattern where you combine periods of eating with periods of extended fasting. There are a lot of different types of intermittent fasting, that mostly vary by the amount of time spent fasting and the amount of time eating. Richie Kirwan, an expert in nutrition talks us through the examples.
Who should try this way of dieting and is it easy? Richie tells us in this video.
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Chapters:
00:00 - What is intermittent fasting?
02:40 - Why is it popular?
03:48 - Does intermittent fasting work?
05:16 - How easy is intermittent fasting
06:00 - Ketones
07:00 - Over eat on intermittent fasting?
07:37 - Does it stunt muscle growth?
09:37 - Who should try intermittent fasting?
10:57 - Any more diet questions?
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0:00
what the hell is intermittent fasting
0:02
and is it all it's made out to be let's
0:03
talk about that
0:07
how's it going guys my name is richie
0:08
kirwan and today we're going to talk
0:10
about something that has been one of the
0:12
most popular diet trends for the last 10
0:15
years or so intermittent fasting what is
0:17
it how do you do it and is it better
0:19
than plain old dieting before i go any
0:21
further i want to point out that i'm
0:23
only going to be talking about
0:24
intermittent fasting in the context of
0:26
fat loss or muscle gain because those
0:28
are by far the most popular reasons
0:30
people look into it i will talk about
0:32
some of the potential health benefits of
0:33
if but they won't be my focus so first
0:36
off what even is intermittent fasting
0:38
well there are a few different types but
0:40
at its heart iaf is an eating pattern
0:43
where you combine periods of eating with
0:45
periods of extended fasting to put
0:47
things in context the longest period of
0:49
fasting that most people experience is
0:51
the overnight fast between the last meal
0:54
and breakfast yes the first meal of the
0:56
day is literally the meal where you
0:58
break your fast in the english language
1:00
at least now there are a lot of
1:02
different types of intermittent fasting
1:03
that mostly vary by the amount of time
1:05
spent fasting and the amount of time
1:07
eating so here are a few examples
1:09
probably the simplest form of fasting is
1:11
known as alternate day fasting and this
1:13
is where people eat one day and fast at
1:16
the next pretty simple right another
1:17
very popular type of fasting is five two
1:19
fasting this is where someone eats
1:21
normally for five days a week and they
1:23
fast for two days a week there are also
1:24
versions of this where people don't
1:26
completely fast on the fast days but
1:28
have a very small amount of calories
1:30
maybe four or five hundred to help with
1:32
hunger so yeah it's not really fasting
1:34
but they call it modified fasting one
1:36
type of fasting that has become
1:38
incredibly popular in the last few years
1:40
is 16-8 fasting which is made really
1:42
popular by martin burkin and his lean
1:45
gains method in 16-8 fasting you fast
1:47
for 16 hours a day and you have an
1:49
eight-hour feeding window in practice
1:51
for some people this can be as easy as
1:53
skipping breakfast and waiting until
1:54
lunch time to have your first meal of
1:56
the day to be more exact this type of
1:58
fasting is actually called time
2:00
restricted feeding or trf because you
2:03
limit the feeding window to specific
2:04
times of the day there's also a type of
2:06
time restricted feeding called omad or
2:08
one meal a day and you guessed it you
2:11
only eat once a day and spend the rest
2:13
of the time fasting and just as an
2:15
interesting side note some people like
2:16
to claim that while they're fasting they
2:18
take some branched chain amino acids or
2:20
medium chain triglycerides to help fuel
2:21
workouts i hate to break it to you
2:23
though if you're eating any type of
2:25
macronutrient protein like bcaas fat
2:28
like mct oil carbs you're breaking your
2:30
fast does it matter practically not
2:32
really but it's worth clarifying because
2:34
people really get hung up on when a fast
2:36
is actually broken so why has
2:38
intermittent fasting become so popular
2:40
well if you've ever watched any of my
2:42
previous videos on weight loss and if
2:44
you haven't you really should check them
2:45
out now you'll know that for weight loss
2:46
to happen you need a calorie deficit
2:49
meaning you need to be eating fewer
2:50
calories than you burn intermittent
2:52
fasting is a form of automatic calorie
2:55
restriction that's something that can
2:57
help you reduce your calories without
2:59
actually having to count calories like
3:01
cutting out carbs or avoiding processed
3:03
foods you see if you limit the time you
3:05
can eat you limit the amount of calories
3:07
you eat which can lead to weight loss
3:09
and this is the point where i crush a
3:11
lot of your dreams by telling you what
3:12
you don't want to hear when it comes to
3:14
weight loss there is no magic to
3:16
intermittent fasting you see a lot of
3:18
people have got into their head that
3:20
intermittent fasting allows you to eat
3:22
as much as you want during your feeding
3:24
window as long as you fast when you're
3:26
supposed to nothing could be further
3:28
from the truth intermittent fasting
3:29
works the exact same way as every other
3:32
diet works by reducing the calories that
3:34
someone eats how do we know that well
3:36
luckily there have been a number of
3:38
trials that have compared intermittent
3:40
fasting with standard daily calorie
3:42
deficits otherwise known as continuous
3:44
energy restrictions so what does the
3:46
science say exactly intermittent fasting
3:48
works but its effects aren't any better
3:51
than regular dieting when calories are
3:53
controlled now before i get assaulted in
3:55
the comments section for saying
3:56
intermittent fasting doesn't work that's
3:58
not what i'm saying at all they
4:00
absolutely do work but there's no magic
4:03
to intermittent fasting diets and they
4:05
just work just like every other diet in
4:07
existence by creating a calorie deficit
4:09
on top of having similar weight loss
4:11
results intermittent fasting also seems
4:13
to result in similar improvements in
4:14
different markers of cardio metabolic
4:16
health compared with continuous calorie
4:18
restriction like cholesterol
4:19
triglycerides and markers of
4:20
inflammation in fact a recent trial with
4:23
139 participants using early trf where
4:26
people only ate between 8 a.m and 4 p.m
4:29
found that both the trf and the normal
4:32
calorie restriction groups lost the same
4:34
amount of weight and got the same
4:36
improvements in blood lipids and other
4:38
metabolic markers there were no
4:40
significant differences between the
4:42
groups now while that sounds negative
4:44
it's actually really good and shows that
4:47
intermittent fasting is a viable option
4:49
for people who want to improve their
4:51
health and lose some weight that said
4:53
there have been some studies that have
4:55
shown differences between intermittent
4:56
fasting and continuous calorie
4:58
restriction and have shown slightly
4:59
different effects on some metabolic
5:01
markers but we need a lot more research
5:03
before we can say anything about them
5:05
for sure so that might make you ask why
5:07
has intermittent fasting become so
5:09
effective and so popular well there are
5:11
a few practical reasons that make it a
5:13
really easy diet to follow for some
5:15
people first off it's very easy to
5:18
implement there doesn't have to be any
5:19
calorie counting if you don't want to
5:21
you don't have to change the foods that
5:22
you eat you just eat the same food you
5:24
normally eat but you just have less time
5:26
to do it for example one pilot study
5:28
just told the participants to eat
5:30
breakfast an hour and a half later and
5:32
dinner an hour and a half earlier for 10
5:35
weeks they gave them no other
5:36
instructions that was the only diet
5:39
advice they received and over the course
5:41
of 10 weeks they automatically ate fewer
5:44
calories but lost weight easier you make
5:46
a diet the more likely people are going
5:48
to be able to stick to it and have
5:50
success another thing that makes
5:52
intermittent fasting easy and convenient
5:54
is that you have fewer meals to worry
5:55
about and to cook for if you're doing
5:57
time restrictive feeding you don't need
5:58
to worry about eating and cleaning up
6:00
breakfast in the morning you just wake
6:01
up and go another possible benefit of
6:03
intermittent fasting especially the
6:05
alternate day or extended fasting is
6:07
that when you haven't eaten for a while
6:08
your body produces ketones which it uses
6:11
as a fuel source which may actually help
6:13
to reduce appetite if people are less
6:15
hungry they're also less likely to
6:17
overeat and something that people love
6:19
about intermittent fasting or
6:20
specifically time restricted feeding is
6:22
that it can allow you to have fewer but
6:25
larger more satisfying meals instead of
6:27
more
6:28
small meals this alone can be enough for
6:31
some people who are sick of the little
6:33
and often meal mentality that said
6:35
intermittent fasting comes with its fair
6:38
share of problems too first off it can
6:40
be very difficult to fit around a social
6:42
life skipping breakfast is usually fine
6:44
but if you don't eat after 7pm in the
6:46
evening and your friends want to go out
6:47
for dinner at eight it's going to suck
6:49
while you sip your sparkling water while
6:51
you longingly watch them chow down on
6:53
some juicy burgers some delicious onion
6:55
rings and a nice big slice of cheesecake
6:57
for dessert who needs friends right
6:59
another issue with intermittent fasting
7:00
is something i mentioned earlier it's
7:02
still possible to overeat during your
7:05
eating window and that can completely
7:06
wipe out the calorie deficit you created
7:08
while fasting like i said some people
7:10
have got it into their heads that it
7:12
doesn't matter how much you eat during
7:14
your feeding window but the truth is
7:16
calories still matter there is some
7:19
research that some people may actually
7:21
eat more and even move less when they
7:24
know that they have a day of dieting
7:26
coming up again this can potentially
7:28
defeat the whole purpose of the fast
7:31
that's it this brings me to another
7:32
issue with intermittent fasting as it
7:34
relates to the second most common use
7:36
for it muscle gain you see a common
7:38
question is whether intermittent fasting
7:39
can be used for bulking or lean gaining
7:42
and my answer is yes but it's probably
7:44
not ideal you see if you watched any of
7:47
my videos on bulking or protein timing
7:48
and distribution and if you haven't
7:50
remember to check them out after this
7:51
one you'll know that two of the most
7:53
important factors for muscle gain are
7:55
getting enough calories and getting
7:56
regular protein feedings as i've already
7:59
mentioned fasting no matter what type
8:01
you do makes it harder to get enough
8:03
calories and if you're a hard gainer
8:05
it's likely that you don't eat enough
8:06
calories as it is so intermittent
8:08
fasting isn't going to help you with
8:09
that but on top of that i've also spoken
8:11
about how important it is to get regular
8:13
doses of enough high quality protein to
8:16
stimulate muscle protein synthesis after
8:19
training muscle protein synthesis is the
8:21
process that your body uses to build
8:22
more muscle and you can stimulate it
8:24
after resistance exercise for up to 24
8:26
or maybe even 48 hours the more you can
8:29
stimulate mps in theory the more muscle
8:32
you can potentially build if you go for
8:33
long periods without eating you're
8:35
losing out on opportunities to stimulate
8:38
muscle growth that's not to say you
8:39
can't build muscle while fasting you
8:41
absolutely can and we have evidence from
8:44
a few studies to show just that and it
8:46
seems just as effective as regular
8:48
dieting for muscle retention the thing
8:50
is when it comes to absolutely
8:51
maximizing your muscle gains more
8:53
frequent protein feedings are
8:55
potentially a better option again i'm
8:57
not saying you can't build muscle while
8:59
intermittent fasting i'm just saying it
9:00
may not be the most efficient way of
9:03
doing it and one more thing worth
9:04
mentioning a lot of people like to
9:06
mention that when you fast your body
9:08
starts producing more growth hormone and
9:10
this actually helps with building muscle
9:11
so it is true that your body produces
9:14
more growth hormone while fasting but
9:16
and it's a really big butt the levels of
9:18
growth hormone released by your body
9:20
during a fast aren't actually high
9:21
enough to have any benefit on long-term
9:24
muscle growth on top of that growth
9:25
hormone is actually more important for
9:28
long bone growth when you're young than
9:30
it is for muscle size so now that we've
9:32
cleared up the confusion around some of
9:34
the aspects of intermittent fasting who
9:35
should actually try it so here's the
9:36
thing it really depends on the
9:38
preference of the individual some people
9:40
absolutely love intermittent fasting
9:42
because it's really easy for them to fit
9:44
into their lifestyles often these are
9:46
people that don't get hungry in the
9:47
morning and don't mind skipping
9:48
breakfast or people who have really busy
9:50
lifestyles that make skipping meals easy
9:53
or you know people without social lives
9:55
while preferring one way of eating over
9:58
another doesn't sound particularly
9:59
important it absolutely is you see at
10:02
the end of the day the specific diet you
10:04
follow only matters if you can actually
10:06
stick to it and this is called dietary
10:08
adherence if intermittent fasting helps
10:10
someone to stick to their diet better
10:11
than other ways then that's reason
10:13
enough to do it never forget the
10:15
importance of adherence for anything for
10:17
your diet or your exercise on the other
10:19
hand some people just can't do
10:21
intermittent fasting at all if you're
10:23
the kind of person that skips breakfast
10:24
only to get ravenously hungry at 10 a.m
10:26
and ends up eating 10 slices of toast
10:28
and half a box of cereal to make up for
10:30
it fasting probably isn't for you on top
10:32
of that there are also people suffering
10:34
from disordered eating like people who
10:35
regularly binge and restrict or people
10:37
with really poor relationships with food
10:39
for people like that intermittent
10:41
fasting is probably not a good idea an
10:43
eating pattern that helps you to develop
10:45
a healthier more consistent relationship
10:47
with food is probably much better the
10:49
easiest way to find out if it works for
10:51
you is to try it for a week or two if it
10:53
works great if it doesn't
10:56
at least just try it so i hope that
10:57
cleared everything up for you about
10:58
intermittent fasting as always if you
11:00
have any more questions let me know in
11:02
the comments below and let us know about
11:03
your own experiences with intermittent
11:05
fasting remember to hit the like button
11:06
and to subscribe to the my protein
11:08
youtube channel for more great
11:09
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11:17
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