Up next in 10
Expert nutritionist Dr Richie Kirwan explains how protein intake influences muscle growth and answers some of the most common questions about building muscle.
In this video, we’re going to take an in-depth look at the role protein plays in muscle gain and how much you really need to maximise your results.
Dr Richie Kirwan answers some important questions like, how much protein should you eat to build muscle? Is there a limit to how much protein your body can use in one meal? And does eating more protein automatically lead to more muscle growth?
There are a lot of myths and misconceptions surrounding protein intake, and Richie is going to break down the science behind protein and muscle gain so you can make more informed decisions about your nutrition and training.
Show More Show Less View Video Transcript
0:00
Do you ever get confused by all the
0:01
different recommendations you see about
0:02
protein? Not sure how much you actually
0:04
need if you want to build muscle? Well,
0:06
in this video I'm going to try and
0:07
explain exactly what you need to know
0:10
about protein intake and muscle gain.
0:15
>> [music]
0:16
>> How's it going guys? My name's Richie
0:17
Kirwan. I'm a registered nutritionist, a
0:19
nutrition researcher, and a university
0:21
nutrition lecturer. Before we start, I
0:23
just want to point out that we're not
0:24
recommending any particular protein
0:26
supplements here. What I'm going to do
0:27
is explain how protein works in general
0:29
and why the amount you eat actually
0:31
matters. So, let's get started. Let's
0:33
begin by clearing the air around the
0:34
recommended daily intake of protein,
0:36
which is advised by the World Health
0:38
Organization and most governments
0:39
worldwide. The recommended amount
0:41
depends on your body weight because if
0:43
you're bigger and have more muscle,
0:44
you'll usually need a little more
0:45
protein to maintain it. Now, in this
0:47
video we're going to mention quite a few
0:49
numbers, but don't worry, I'll explain
0:51
how to apply them to yourself as we go
0:52
along. When we talk about grams per body
0:54
weight, I'm talking about people who are
0:56
more or less in the normal body weight
0:59
category, even though I'm not crazy
1:01
about that term. Now, if you have a lot
1:03
of body fat and you calculate your
1:04
protein intake based on your total body
1:06
weight, you can end up with a very high
1:08
number.
1:09
So, instead, you can roughly estimate
1:12
your lean or healthy body weight using
1:14
your height and a body mass index of
1:16
about 25. The reason I say "healthy" in
1:19
air quotes is because your weight alone
1:21
doesn't determine your health, but BMI
1:23
is still a very commonly used metric and
1:26
it works well for this kind of
1:27
calculation. So, how do you calculate
1:29
your healthy weight? It's really simple.
1:32
You multiply your height in meters
1:34
squared by 25. So, if you are 170 cm
1:38
tall, that's 1.7 m, and your estimated
1:41
lean weight would be 1.7 squared
1:44
multiplied by 25,
1:46
which comes out at about 72.25 kilos.
1:49
This is the method I use to calculate
1:50
protein for most of my clients. Now,
1:52
when I talk about how much protein to
1:53
eat, I'm going to use grams per kilogram
1:55
of body weight. And the World Health
1:57
Organization recommends about 0.8 g of
2:00
protein per kilogram of body weight per
2:02
day, as do most government dietary
2:04
recommendations. So,
2:06
how much is that in real life? Well, if
2:08
you weigh 70 kilos, you just multiply
2:10
your body weight by 0.8, and that tells
2:13
you how much protein you should eat in a
2:14
day. Interestingly, that works out at
2:16
about 56 g of protein. And honestly, a
2:19
lot of people watching this could
2:20
probably eat that much in a single meal
2:22
without too much trouble. Now, the
2:24
reason that recommendation looks so low
2:26
is because it's not a recommendation for
2:28
building muscle. It's a recommendation
2:30
to prevent protein deficiency. In other
2:33
words, it's the amount needed to make
2:35
sure you don't become malnourished, not
2:38
the amount needed to maximize
2:40
performance, recovery, or muscle growth.
2:43
Most government-recommended dietary
2:45
intakes are designed with that in mind,
2:47
and they're there to prevent
2:48
deficiencies across the whole
2:50
population, not to optimize body
2:52
composition or gym performance. In fact,
2:55
newer guidelines are starting to
2:56
recognize that this might be on the low
2:58
side. The most recent dietary guidelines
3:00
for Americans, published in 2026, now
3:02
suggest that adults may benefit from
3:04
somewhere around 1.2 to 1.6 g per
3:07
kilogram of body weight per day,
3:09
depending on the individual. That
3:10
doesn't mean everyone needs that much,
3:12
but it shows that the old recommendation
3:14
was never meant to be the optimal
3:17
amount. It was the minimum. So, in
3:20
reality, the standard recommendation is
3:22
perfectly adequate for basic health. But
3:24
when it comes to building muscle,
3:25
recovering from training, or getting the
3:27
most out of your diet, we can almost
3:29
certainly do better than that. So, there
3:31
are two ways we can think about protein
3:33
intake, and the most common is total
3:35
grams of protein per day. So, there's a
3:38
really popular meta-analysis that I'd
3:40
like to mention. A meta-analysis is
3:42
basically a study where they analyze the
3:43
results of multiple similar studies to
3:45
get a more definite answer. The study is
3:48
by Morton and colleagues, and it
3:50
includes researchers like Brad
3:51
Schoenfeld, Eric Helms, James Krieger,
3:54
and Stu Phillips. It found that about
3:56
1.6 g of protein per kilogram of body
3:58
weight per day seems to provide close to
4:01
the maximum benefit for muscle growth in
4:03
most people who are resistance training.
4:06
So, if you weigh 70 kilos, that works
4:08
out at about 112 g of protein per day.
4:10
Based on that analysis, eating more than
4:12
this probably won't lead to much extra
4:14
muscle gain for most people. Now, a lot
4:15
of you probably think that sounds quite
4:17
low, especially if you lift weights
4:19
regularly. And it's important to
4:20
remember that this is just one
4:22
meta-analysis. It's useful, but it
4:24
doesn't necessarily represent the final
4:26
word on the topic. And newer research
4:27
suggests the story might be a little
4:29
more nuanced. So, before I give that as
4:32
my final recommendation, I want to talk
4:34
about another way of thinking about
4:35
protein intake, which is protein per
4:37
meal, not just protein per day. Protein
4:40
per meal used to be thought of as a more
4:42
useful way of looking at things because
4:44
of something called the leucine
4:46
threshold. Leucine is one of the
4:47
essential amino acids. Actually, it's a
4:49
branched-chain amino acid, and it plays
4:51
a key role in stimulating muscle protein
4:53
synthesis, which is the process your
4:55
body uses to build new muscle tissue. If
4:57
you get enough leucine in a single meal,
4:59
you can maximally stimulate muscle
5:01
protein synthesis. And once that signal
5:03
is fully switched on, eating more
5:04
protein in the same meal probably won't
5:06
increase muscle protein synthesis
5:08
any further. Research suggests that for
5:10
most people, a mixed meal containing
5:13
roughly 0.3 to 0.4 g of protein per
5:15
kilogram of body weight is enough to
5:17
reach this leucine threshold and
5:19
maximally stimulate muscle protein
5:21
synthesis. So, if you weigh 70 kilos,
5:23
that works out at around 25 to 30 g of
5:25
protein in a meal. And if you eat four
5:27
meals like that across the day, you end
5:28
up at roughly 1.6 g per kilograms per
5:31
day, which is exactly the same number we
5:33
got from the meta-analysis. So, at first
5:35
glance, both ways of looking at protein
5:37
intake seem to point to the same place.
5:39
Finally, you may have heard somewhere
5:41
that you can only digest about 20 to 25
5:43
g of protein in a single meal, and that
5:45
anything more than that is wasted. Like
5:47
a lot of nutritionists, there's a small
5:50
grain of truth in it, but the way it's
5:52
usually explained is wrong. We do know
5:55
from controlled studies that in young,
5:56
healthy people, around 20 g of
5:58
high-quality protein is often enough to
6:00
almost maximally stimulate muscle
6:02
protein synthesis after exercise. If you
6:04
double that amount of 40 g, you don't
6:06
double muscle protein synthesis, but
6:08
some studies show you can increase it a
6:10
little bit further, maybe by another 10
6:13
or 20%. But, that absolutely does not
6:16
mean the rest of the protein is wasted.
6:18
Some of that extra protein can be
6:19
oxidized for energy, but amino acids are
6:21
also used to build other tissues in the
6:23
body and to make hormones, enzymes,
6:25
immune proteins, and all sorts of other
6:27
things that your body needs every day.
6:29
Larger amounts of protein per meal may
6:31
also extend the muscle protein synthesis
6:33
response for multiple hours after you
6:36
eat. On top of that, resistance exercise
6:38
makes your muscles more sensitive to
6:39
protein, which means after training, you
6:42
may be able to get a bigger muscle
6:43
protein synthesis response from a larger
6:45
protein dose than you would at rest. So,
6:48
if you eat more than 25 g of protein in
6:50
a meal, don't worry. Your body can
6:52
digest it, absorb it, and use it. It
6:55
just might not all go directly into
6:56
muscle at the exact moment. Now, back to
6:59
how much protein per meal. So, if four
7:01
meals works well for you, you might be
7:02
wondering, would eating more meals be
7:04
even better? This is where we have to
7:05
look at what's called mechanistic data.
7:07
In other words, studies looking at the
7:09
biology of how muscle protein synthesis
7:11
actually works. From early research, we
7:13
know that after you stimulate muscle
7:15
protein synthesis with a dose of
7:16
protein, there is a period of time where
7:18
the muscle becomes less responsive to
7:20
another dose. This is sometimes called
7:22
the refractory period. In a lot of early
7:25
studies, this seemed to last roughly 3
7:27
to 5 hours, meaning that people assumed
7:29
that after you maximally stimulate
7:31
muscle protein synthesis, you need to
7:32
wait a while before another meal can
7:34
fully stimulate it again. Based on that
7:37
idea, some researchers suggested that
7:39
spacing protein doses every few hours
7:41
might be the best [music] way to keep
7:43
muscle protein synthesis elevated across
7:45
the day. If we assume you're awake for
7:47
about 16 hours, which you probably
7:49
should be if you're sleeping properly,
7:51
that means you could theoretically fit
7:53
in five or six protein feedings per day.
7:56
Now, if each of those meals contained
7:57
about 0.4 g of protein per kilogram of
7:59
body weight, that would bring your total
8:01
daily intake up to around two to 2.4 g
8:04
per kilogram per day. Interestingly,
8:06
there is some evidence that intakes in
8:08
this range can be beneficial in very
8:11
lean athletes, bodybuilders, or people
8:14
training at a very high level,
8:16
especially when calories are restricted.
8:19
So, the idea of higher protein intakes
8:21
isn't completely unrealistic, even if
8:23
it's based partly on theoretical models
8:25
of how muscle protein synthesis works.
8:27
That's it. You should ask yourself
8:29
realistically, do you fit into any of
8:31
the groups I just mentioned?
8:32
Very lean athletes, bodybuilders, people
8:35
training at high level,
8:37
and especially when calories are
8:39
restricted. If not, it might not be
8:40
relevant for you,
8:42
as much as you might want it to be. If
8:44
you're serious about building muscle, a
8:45
very solid starting point is around 1.6
8:47
g per kilogram per day, spread across
8:50
about four meals, each containing
8:51
roughly 0.4 g per kilogram. For most
8:54
people, that's already going to be very
8:56
close to optimal. If you really want to
8:58
push things as far as possible, you
9:00
could experiment with slightly higher
9:01
intakes, maybe up to 2.2 or 2.4 g per
9:04
kilogram per day, spread across more
9:06
meals. But, this takes more planning,
9:08
more organization, and honestly, there
9:11
just isn't enough real-world evidence to
9:13
support this kind of recommendation for
9:15
most people. Personally, I think four
9:17
meals per day is a really good balance
9:19
between optimizing muscle growth and
9:20
still having a normal life that doesn't
9:23
revolve entirely around your food
9:25
schedule. And if four meals is out of
9:27
the question, three is probably
9:28
perfectly fine as well. So, in practice,
9:31
the sweet spot for most people is
9:32
probably somewhere between 1.6 and 2.4 g
9:35
of protein per kilogram of body weight
9:37
per day. Depending on the person, their
9:39
training, and their goals. Now, before
9:41
you start setting alarms for every 3
9:42
hours to drink protein shakes, there's
9:44
one more thing we need to talk about
9:46
because newer research suggests that the
9:48
story might not be quite as simple as we
9:51
said here. A lot of early studies that
9:53
gave us the idea of a leucine threshold
9:55
and a refractory period only looked at
9:58
muscle protein synthesis for a few hours
10:00
after eating, and they often used
10:02
relatively moderate doses of protein,
10:04
usually around 20 to 40 g. Like I
10:06
mentioned, based on those studies, it
10:08
looked like once you hit a certain
10:09
amount of protein in a meal, muscle
10:10
protein synthesis reached maximum, and
10:12
eating more than that didn't seem to do
10:14
much extra. But, more recent research
10:17
has started to show that this might not
10:19
be the full picture. In another recent
10:21
study from Luke Van Loon's research
10:23
group in the Netherlands, participants
10:24
consumed a very large dose of protein in
10:27
a single meal, about 100 g, after
10:30
resistance exercise.
10:32
What the researchers found was that
10:33
muscle protein synthesis stayed elevated
10:36
for much longer than expected, up to 12
10:39
hours, way beyond what had been seen in
10:42
earlier studies. This suggests that
10:44
muscle protein synthesis doesn't
10:46
necessarily just switch off after a
10:48
certain amount of protein, and that
10:49
larger protein doses may continue to
10:52
support muscle building for longer than
10:54
we originally thought. So, instead of
10:56
thinking about muscle protein synthesis
10:57
as something that turns on and off every
10:59
few hours like a light switch, it might
11:01
be more accurate to think of it as a
11:02
response that can stay elevated for
11:05
quite a long time, especially after hard
11:08
training and when enough protein is
11:10
available. What this means in practice
11:12
is that the older idea of needing
11:14
perfectly spaced meals every 3 hours is
11:16
probably not as strict as we once
11:18
thought. And it also means that eating
11:20
larger amounts of protein in fewer meals
11:23
can still work [music] pretty well.
11:24
Another thing we need to consider is
11:26
that muscle protein synthesis doesn't
11:27
just increase for a short time after a
11:29
workout and then switch off. After a
11:31
full resistance training session,
11:33
especially one that involves a lot of
11:35
muscle mass, and by that I mean a full
11:36
body workout, muscle protein synthesis
11:39
can stay elevated for up to 24 to 48
11:42
hours, particularly in people who are
11:44
newer to training. And during that time,
11:46
every time you eat protein, you further
11:48
stimulate muscle protein synthesis on
11:50
top of the already elevated level. So,
11:53
instead of thinking about muscle growth
11:54
as something that only happens in a
11:55
short window after a meal, it's probably
11:57
more accurate to think of it as a
11:59
process that stays elevated for a long
12:01
period after training, and that can be
12:03
boosted multiple times by feeding during
12:06
that time. This is one of the reasons
12:08
why total daily protein intake seems to
12:10
matter so much, because your muscles
12:12
stay sensitive to protein for a long
12:15
time after you train. This is one of the
12:17
reasons why total daily protein intake
12:18
seems to matter so much, because your
12:20
muscles stay sensitive to protein
12:22
[music] for a long time after you train.
12:24
So, now that you know how much protein
12:26
you probably need, I want to leave you
12:27
with one last reminder. It doesn't
12:29
matter if how much protein you eat if
12:31
you're not putting in the work in the
12:34
gym. The stimulus for muscle growth
12:36
comes from resistance training, and
12:38
protein just provides the building
12:40
blocks to support that process. If you
12:42
don't give your muscles a reason to
12:43
grow, no amount of protein powder in the
12:46
world is going to get you jacked. In
12:49
reality, most of the research suggests
12:51
that somewhere around 1.6 g per kilogram
12:53
per day is a very good target for most
12:55
people. But, that can change depending
12:56
on your training, your body size, and
12:58
how serious you are about maximizing
13:00
muscle growth.
13:01
>> [music]
13:01
>> Depending on those, you might benefit
13:02
from a bit more, especially if you
13:04
spread your protein across the day, and
13:06
make sure each meal contains enough to
13:08
properly stimulate muscle protein
13:09
synthesis. So, don't stress too much
13:12
about hitting an exact number. Focus on
13:14
training hard, eating enough total daily
13:16
protein, and getting it in regularly
13:19
across the day, and you'll be covering
13:21
the things that actually matter. What do
13:22
you think? Did that clear up some of the
13:24
confusion around protein intake? As
13:26
always, if you have any questions, let
13:27
me know in the comments below, and
13:29
remember to like and subscribe to the
13:31
Myprotein YouTube channel for more great
13:33
evidence-based nutrition information.
#Sports