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Does Muscle And Fat Change Your Appetite? | Nutritionist Explains... | Myprotein
Jan 30, 2025
Can the amount of muscle and fat you have on your body change your appetite and what happens if you lose weight?
Lots of people have tried to lose weight at some point in their lives and unfortunately some have tried and failed many times. It’s really easy to assume that they might have been following the wrong diet or even worse, to think that they weren’t disciplined enough but the truth is, trying to lose weight is a battle against one of the most powerful adversaries we’ll ever face: our own brains.
Richie Kirwan, nutritionist expert tell us the important role that your muscle, body fat and even bone have in keeping you from getting hungry.
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Chapters:
00:00 - Intro into Muscle, Body Fat and Appetite
01:38 - Body fat and lipostat
03:12 - The science
05:28 - Muscle and appetite
06:10 - What is Myostatin?
06:59 - Got any more appetite questions?
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0:00
can the amount of muscle and fat that
0:01
you have in your body change your
0:02
appetite and what happens if you lose
0:04
weight let's talk about that
0:08
how's it going guys my name is richie
0:09
kirwan and today we're going to talk
0:10
about some of the ways that your body
0:12
regulates its appetite and the important
0:15
role that your muscle body fat and even
0:17
bone have in keeping you from getting
0:19
hungry lots of people have tried to lose
0:21
weight at some point in their lives and
0:23
unfortunately some have tried and failed
0:25
many times it's really easy to assume
0:28
that they might have been following the
0:29
wrong diet or even worse to think that
0:31
they weren't disciplined enough but the
0:33
truth is
0:34
trying to lose weight is a battle
0:36
against one of the most powerful
0:39
adversaries we'll ever face
0:41
our own brains you see your brain is
0:44
wired through billions of years of
0:47
evolution to seek out food no matter how
0:49
much you might want to get ready for
0:51
bikini season i've spoken about some of
0:52
the reasons in my video on why losing
0:54
weight is so hard so remember to check
0:56
that out after this video and if you're
0:58
really interested you could check out
0:59
the book the hungry brain by stefan
1:01
giene which goes into incredible detail
1:04
on how our brain makes eating less a lot
1:07
harder especially in the modern world
1:09
with 24 7 access to delicious calorie
1:12
dense food the fact that there are whole
1:15
books written on this means that
1:17
appetite control is a really complex
1:20
topic that i couldn't hope to cover in
1:23
just one video but instead i'm going to
1:25
talk about how changes in your level of
1:27
muscle mass and body fat can cause
1:29
changes in your appetite that might make
1:31
dieting a whole lot harder we'll also
1:33
talk about how even your bones might
1:35
have a whole role to play themselves in
1:37
controlling how much you eat first off
1:39
let's talk about body fat and the
1:41
concept of the lipostat lipo comes from
1:43
the greek word for fat and stat as in
1:46
the word thermostat something that helps
1:48
us to maintain a constant state so body
1:50
fat produces a hormone called leptin
1:53
and more body fat you have generally the
1:55
more leptin you produce in healthy
1:57
people leptin actually causes us to eat
1:59
less
2:00
it does this by affecting the
2:02
hypothalamus the part of the brain that
2:04
helps to control appetite when leptin
2:07
was first discovered there was actually
2:08
a lot of excitement about it because
2:10
people thought it might be possible to
2:12
control appetite just by injecting
2:14
people with leptin unfortunately
2:16
experiments trying to do just that never
2:18
actually worked out in humans but you
2:19
might ask what about people with a lot
2:21
of body fat why doesn't leptin stop them
2:23
from eating too much that's one of the
2:25
reasons appetite control is so complex
2:27
we know that in people with obesity they
2:29
have very high levels of leptin but they
2:32
also suffer from something called leptin
2:34
resistance this means their bodies have
2:36
been exposed to high levels of leptin
2:38
for so long that they've lost their
2:40
sensitivity to it it's kind of similar
2:42
to how people become insulin resistant
2:43
and don't react to insulin in the same
2:45
way on the other hand if people lose a
2:47
lot of body fat or even if they just
2:48
drop calories for a while leptin levels
2:50
can drop and this causes appetite to
2:53
increase and we want to eat more we also
2:55
know that you can temporarily increase
2:57
leptin by eating more especially by
2:58
eating carbohydrates but it's a very
3:00
short-lived increase so it doesn't
3:02
really help someone who's trying a
3:03
longer term low calorie diet or trying
3:05
to maintain weight loss another possible
3:07
way our body can regulate our body
3:08
weight strangely enough might be through
3:10
our bones so i want to talk about one of
3:12
the best research studies i've read in
3:14
the past few years the only problem with
3:15
it is that it was done in mice which
3:17
might make you think that it doesn't
3:19
apply to humans but we'll talk about
3:21
that in a minute so in the original
3:22
experiment some researchers in sweden
3:25
surgically implanted tiny weights into
3:27
some mice to artificially make them
3:29
heavier over the course of about two
3:31
weeks the mice with the added weight
3:33
lost weight
3:34
from their body fat compared to mice
3:36
that didn't have any weights at it that
3:37
was an interesting fighting by itself so
3:39
the researchers wanted to find out why
3:41
it happened through a few different
3:42
experiments they found out that the mice
3:44
with added weights were eating less and
3:46
they also found out that the reason they
3:48
were eating less had nothing to do with
3:50
leptin but that wasn't enough for the
3:52
researchers so they did even more
3:53
experiments and found out that the
3:55
weight loss effect didn't happen in mice
3:57
that were missing a specific type of
3:59
bone cell called osteocytes the
4:01
researchers came up with the idea that
4:02
the osteocytes in the mice's leg bones
4:05
were able to detect changes in body
4:07
weight this means that when the
4:08
scientists added the weights to mice the
4:10
bone cells detected the extra weight and
4:12
sent a signal to the mouse's brain
4:14
basically saying hey we feel we're too
4:16
heavy right now time to eat a little
4:17
less and get the weight down the
4:19
research team call this weight control
4:20
system the gravitostat because of the
4:22
force of gravity is helping to control
4:24
body weight what's interesting is that
4:26
in the modern world a lot of people
4:28
spend most of their life sitting down
4:30
which means bone cells in their legs
4:32
don't get much opportunity to detect
4:34
their body weight and might not be able
4:36
to help them regulate appetite all that
4:38
well however that's a very early theory
4:40
at the moment and needs more evidence so
4:43
the scientists decided to try and see if
4:44
they could do something similar in
4:46
humans what they did is they got a group
4:48
of participants with obesity to walk
4:50
around with weighted vests that were
4:52
about 11 percent of their body weight
4:53
which means 100 kilogram person would
4:55
wear an 11 kilogram vest for eight hours
4:57
a day for three weeks what they found is
5:00
that the participants in the weighted
5:01
vests lost more body weight and body fat
5:05
but not muscle mass compared to a
5:06
control group with no weighted vests the
5:08
researchers think but don't know just
5:10
yet that this weight loss may be due to
5:13
reduce appetite and not you to burning
5:15
more energy just walking around with the
5:17
added weight now these are just a couple
5:19
of experiments but it gives you an idea
5:21
of how animal research can be used to
5:23
design human research and give us an
5:25
idea of another way our bodies are able
5:27
to regulate our body weight finally
5:29
there's another way that our body might
5:30
control our appetite through how much
5:32
muscle we have there's no official name
5:34
for this so i'm calling it the sarcostat
5:36
from the greek word sarc meaning flesh
5:38
or muscle so think of it like this when
5:40
people lose weight they often lose a
5:42
combination of body fat and muscle mass
5:44
unless they do plenty of resistance
5:46
exercise to hold on to it we've already
5:47
mentioned that the loss of body fat
5:49
leads to a drop in leptin that can
5:50
increase appetite well it turns out that
5:52
the loss of muscle mass might have the
5:54
same effect when our level of muscle
5:56
mass shrinks we can see a change in
5:58
certain hormones that are produced in
5:59
our muscles firstly the amount of
6:01
ghrelin produced in our muscles goes up
6:03
ghrelin is a hormone that acts on the
6:05
hypothalamus in the brain to stimulate
6:07
appetite and make us eat more secondly
6:10
less muscle can lead to a decrease in a
6:11
protein messenger called myostatin
6:13
myosin is a pretty well known molecule
6:15
because it actually stops muscle growth
6:17
and genetic mutants that don't produce
6:19
myostatin are known to have huge muscles
6:22
just google myostatin mutant bull or
6:25
mouse and
6:26
you'll see some incredible photos so
6:28
when myostatin goes down another
6:30
molecule called insulin-like growth
6:32
factor goes up and this also affects the
6:34
hypothalamus in the brain increases
6:36
appetite and causes us to eat more the
6:38
possible reason for this is that our
6:40
body is trying to maintain our muscle
6:41
mass and when it detects a sudden drop
6:43
in muscle mass it makes us eat more so
6:45
that we can put on some weight and
6:46
hopefully regain that loss muscle the
6:48
drop in myostatin would help with this
6:50
extra muscle gain too could this mean
6:51
that having more muscle is a good idea
6:53
to reduce appetite we honestly don't
6:55
know because we need a lot more research
6:57
to figure that out so there you have
6:59
three possible ways that different
7:01
tissues in our body our fat our bones
7:03
and our muscle can affect our appetite
7:06
and cause changes in our body weight
7:07
like i said earlier there really are
7:09
many more ways that our body regulates
7:12
appetite and how much we eat and they're
7:13
all incredibly complex with more
7:15
research we'll probably discover even
7:17
more systems of appetite control so what
7:19
do you think
7:20
i know that was a more sciency
7:22
theoretical kind of look at appetite but
7:24
i hope you found it interesting as
7:25
always if you have any questions let me
7:26
know in the comments below and remember
7:28
to like and subscribe to the my protein
7:29
youtube channel for more great
7:31
evidence-based nutrition information
7:36
[Music]
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