---
title: 'I Tested 3 Muscle Building Diets, Only 1 Was Worth It'
source: 'https://youtube.com/watch?v=D6Qw2dfrFRg'
video_id: 'D6Qw2dfrFRg'
date: 2026-07-28
duration_sec: 1070
channel: 'Jeremy Ethier'
---

# I Tested 3 Muscle Building Diets, Only 1 Was Worth It

> Source: [I Tested 3 Muscle Building Diets, Only 1 Was Worth It](https://youtube.com/watch?v=D6Qw2dfrFRg)

## Summary

This video documents a 90-day experiment testing three popular muscle-building diets—main gaining, lean bulk, and fast bulk—on the creator's brother-in-law, Dayton. Using DEXA scans and other measurements, the video compares muscle and fat gains for each diet and provides practical recommendations based on the results.

### Key Points

- **Experiment Overview** [00:23] — The experiment tests three diets: main gaining, lean bulk, and fast bulk, over 90 days on Dayton, who is at 17% body fat.
- **Setting Up Main Gaining** [01:14] — Maintenance calories are estimated by multiplying body weight in pounds by 13-16. Dayton's maintenance is 2300 calories.
- **Protein Intake Advice** [01:49] — Protein needs are lower than commonly thought; 0.7g per pound of body weight is enough to maximize gains for most people.
- **Unexpected Weight Gain** [03:56] — Dayton gained 2 lbs during the main gaining phase due to stress and holiday eating, which led to swapping the diet order.
- **Lean Bulk Definition** [04:19] — The lean bulk involves adding 250 calories to maintenance, resulting in about 2 lbs of weight gain per month.
- **Lean Bulk Results** [04:45] — After 30 days of lean bulking, Dayton gained an estimated 1.35 lbs of muscle, which is above average compared to study participants.
- **Fast Bulk Setup** [05:31] — The fast bulk involves a 500-calorie surplus (2800 calories for Dayton), leading to more energy and strength gains.
- **Fast Bulk Considerations** [08:07] — Fast bulking works best for beginners; experienced lifters tend to gain more fat than muscle.
- **Fast Bulk Results** [09:36] — Dayton gained 1.8 lbs of muscle during the fast bulk, 30% more than the lean bulk, but also three times more fat.
- **Main Gaining Benefits** [10:29] — Main gaining can be effective for those with body fat to spare, allowing muscle growth while losing fat.
- **Main Gaining Final Results** [15:03] — Dayton gained 1.1 lbs of muscle during the main gaining phase and lost some fat, showing its effectiveness.
- **Final Recommendation** [15:53] — The lean bulk is recommended for Dayton as it balances muscle gain with minimal fat gain, aligning with his goals.

## Transcript

How much muscle can you really build in
just 90 days? And more importantly, how
can you do it without gaining fat? To
find out, I'm testing the three most
popular muscle building diets on my
brother-in-law. So, by the end of this
video, you won't just find out how much
muscle he gains, but which one builds
muscle fastest, which one burns fat
while building muscle, and which diet
completely backfires.
>> This is a bit of a disaster. So, last
year I helped my brother-in-law Dayton
drop from 33% body fat down to his
current body fat of 17%. And now he's
hungry for more.
>> Now that I've cut, I really want to bulk
up, get bigger at all. I'm not getting
fat again. Like, I refuse to get fat
again.
>> So, to help Damon with his goal, I'm
starting him off with our first diet,
maintaining. The theory here is that by
training hard while eating just enough
to maintain your weight, your body is
forced to burn off your body fat to fuel
muscle growth. And to measure if that
actually happens, Dayton's getting DEXA
scans before and after each diet to see
how much his muscle and fat changes. But
because short-term DEXA can be less
reliable, we also took ultrasounds,
skinfold, and circumference measurements
to get a more complete picture of which
diet actually works best. Now, to set up
his main gaining diet, if you take your
body weight in pounds and multiply it by
13 to 16, depending on your activity
level, that's roughly what your body
needs to maintain. But I know from
personally working with Dane for so
long, that his current maintenance is
right at 2300 calories. And this is a
sample day of eating I've created for
him to hit that target. As for protein,
Dne's targeting at least 100 g of
protein per day. Now, while that might
sound low, some new research suggests
that if you're eating enough calories
and you're not bodybuilder level
shredded, then your protein needs aren't
nearly as high as most people think. In
fact, if you take your body weight in
pounds and you multiply it by 0.7,
that's already enough to maximize your
gains, which gives Dayton more room for
carbs to fuel his workouts.
>> I got my veggies, lean protein, and my
carbs. We're 7 days in. My weight hasn't
moved. We're doing good. But what's
going to have no doubt the biggest
impact on his gains is his training. So
I'm having Dayton train 5 days a week
using my personal favorite workout
split. And the plan seems to be working.
He's sending me PRs every workout. And
with his app, we'll be able to see how
much his strength gains from each diet
match up to actual muscle growth. But
just as the going was getting good.
>> All right, guys. Quick update.
So, I just realized that both of my
roommates are moving out, and that
leaves me with only two months to find
replacements.
If I don't find someone, that's going to
leave me with a lot of money to pay all
on my own. And on top of that, my
business is hit a dry spell. It's the
slowest it's been for a long time. So,
that's a lot of stress right now and
it's making it a little hard to stay on
track with the workouts and the diets.
>> With all the added stress, he began
snacking a lot more than usual. And it
also didn't help that this was filmed
during the holidays where he couldn't
resist my mom's Filipino desserts.
>> I got my third plate of the night, a
dessert. It's called ube and then some
sort of rice pudding.
>> But then something happened that might
just end this experiment altogether. Um
my grandpa, he passed away a few weeks
ago uh from cancer and he was a big male
role model for me as uh my dad passed
away when I was seven also from cancer.
So he was my father figure. So
yeah, it was honestly a tough time for
our whole family, but especially for
Dayton. And even though he could have
easily quit the experiment, he stuck it
through, not missing a single workout.
And even though he tried his best to
stay on track with his nutrition, when
he returned for his second check-in on
day 30, the results weren't quite what
we had planned. You actually gained 2 lb
of body weight. Now, the goal was to
maintain your weight as best as
possible, and the next phase, the goal
was actually to gain 2 lb
>> in a month. Oops. Luckily, his
overeating actually lines up perfectly
with the next diet that we had planned,
a lean bulk. That's where you take your
maintenance calories and you bump them
up by about 250, which typically results
in around 2 lb of weight gain per month.
So, we decided to swap the order of his
diets and save the main gain diet for
the very end of our experiment. The good
news is that it seems like those extra 2
lbs went to the right places. Okay.
>> Based on Dayton's results, combined with
the data from our additional
measurements and scans, after 30 days of
lean bulking, he's gained an estimated
1.35 lb of actual muscle. As for whether
that's good or not, in a 2020minut
analysis from a huge number of
short-term training studies,
participants gained roughly 2.4 lb of
actual muscle, but it took them 10 weeks
to do. So, Dayton's definitely above
average. Plus, the last time I seriously
assessed my own rate of muscle gain, it
took me 60 days to put on just half a
pound of muscle. So, Dayton clearly
still has the ability to build muscle
quickly. As for fat gain, based on the
data from his belly skin folds,
ultrasound, and waist measurements, he
did gain some fat, but it wasn't
excessive. So, overall, DNE's lean bulk
was quite the success. But, it does beg
the question, can we speed up his gains
further if we feed him even more? So,
for the next 30 days, we're running a
fast bulk, cranking his daily calories
up to 2800. That's 500 calories more
than his body burns every day.
>> You're probably wondering like where
what types of calories should I be
eating?
>> Yeah, right.
>> You're getting enough protein. So, my
personal recommendation is if you're
going to add calories, let's do it from
just pure carbs.
>> Okay.
>> Cuz that's what's going to give you the
glycogen and the energy that you need in
your workouts. that we can see your
workout performance just like really
really be taken to the next level. So,
it's not like we're taking his diet from
this to this. We're just making small
daily changes so that he gains roughly 4
lb by the end of the next 30 days. I can
have a little bit more rice, a bit more
carbs, some more sauce, but I have to
stay on track. I have to weigh
everything. I can't make the same
mistake I made last time.
>> I'm just hoping he doesn't overdo it.
Yeah, my roommate came back from Mexico
and he came back with a giant bag of
candycoated sugared peanuts. And I love
candy covered peanuts. So, I did crush a
lot of these. But at least Dayton was
putting these extra calories to good
use.
>> So, I think Jeremy's right about upping
the carbs. I've been hitting PR after PR
after PR. I have a lot more energy and
I'm just feeling way stronger. Ding felt
so good that he actually started adding
more sets to his workouts. And normally
studies would never allow for this.
Workouts are kept identical. So the diet
is the only variable, but I honestly
think that misses a huge indirect
benefit of eating more calories, the
extra energy to train harder and longer.
So instead of holding him back, we let
him loose. Whether it leads to more
muscle growth, we'll find out soon. In
the meantime, as his body transformed,
so did his business. His Tik Tok fitness
videos drove traffic to his business
content, and that attention turned into
orders. So, I got some exciting news. My
brother is currently looking for a place
to live and I so happen to be looking
for a roommate. He's really into working
out and we have tons of things in common
and we uh get along really well. So, I
really hope it works out because I need
a roommate.
>> And while Dean's work and roommate
search were improving, he was now
dealing with one major downside of his
fast bulk. I've definitely been noticing
a bit of
extra belly fat. Uh I've gained a little
bit of weight as well in my face. I can
see I've gained just a little bit of
weight. Those are the two spots I always
notice that my my face gets a little
chubbier in my my belly. We'll find out
soon whether that's just in his head or
not. But there are a couple factors that
should be working in Dayton's favor. For
starters, a study on untrained lifters
found that a fast bulk led to huge
muscle gains over the course of 8 weeks
with minimal fat gain. But when that
same fast bulk was tested on more
experienced lifters, most of the extra
weight gain now came from fat rather
than muscle. In other words, fast
bulking seems to work best when your
body can actually use those extra
calories to build muscle. And I learned
this the hard way. When I first started
lifting, I did a dirty bulk. sometimes
even drinking a gallon of milk a day and
it worked. I put on a lot of size
without much fat. But when I tried that
same approach a few years later, it just
made me fluffy and I had to spend months
dieting the fat that I gained with very
little extra muscle to actually show for
it. And while Dayton isn't a total
beginner, as he's still in his first
year of proper training, there's a
possibility that the fast bulk actually
works out the best for him. The last 30
days, you've gained 4 lbs. Okay. What
have you noticed? strength, overall
size. I just feel bigger.
>> I have more energy. I feel strong.
Definitely did. Yeah, I've noticed a
little bit of fat gain, but that was to
be expected.
>> Well, you look fuller, dude. Even just
in this shirt, like your arms,
>> your chest,
>> I feel a lot bigger.
>> And his pull-up strength since day one
has actually doubled. Let's go. One more
up.
Look at this new Zach. You can see it
through the shirt. V taper. You look
like a ninja turtle. As for his muscle
and fat results, Dean gained an
estimated 1.8 lbs of muscle, 30% more
than what he gained during his lean
bulk. But it did come with a trade-off.
This time, he gained three times more
fat than during lean bulk. And I've seen
this quite a bit. People fast ball, they
put on size and fat, and then they hit a
point where the fat gain is so
overwhelming, they never actually cut to
get rid of it. Luckily, Dane was still
looking relatively lean. And with the
extra fat that he gained, it actually
put him in the perfect position to take
another shot at our last diet. Meaning
gaining, which means that you have to
maintain your weight.
No more tons of ground beef. I have to
go back to chicken and jerky. Okay, I I
know what's coming.
>> And while Dayton may not be thrilled
about scaling his calories back, if he
sticks to the plan, he should still be
able to build muscle and instead of
gaining fat, actually lose some. That's
because while muscle growth does require
energy, that energy doesn't have to come
directly from the food you eat, most
people carry well over 100,000 calories
stored as body fat. And your body can
tap into that energy to fuel muscle
growth. In fact, when Dayton first
started working with me on a fat loss
diet, he was still able to build muscle,
not as fast as during his bulk, but at a
pretty solid rate of about 0.7 lbs of
muscle per month. and instead of gaining
fat, he was losing about 5 lbs of pure
fat each month. And he's not some rare
exception. We see it all the time in
studies, and I've seen it countless
times with our app members, even people
who have trained for years. They start
dropping fat while building new muscle
because for the first time in their
lives, they're actually following a
proper plan. And that is exactly what
our app does for you. You enter your
info, it gives you a personalized diet
and training plan so you quickly see
results and then it adjusts your plan
over time based on how your body
responds. And you can try it completely
free for 2 weeks over at
buildwithcience.com or by scanning this
QR code right here. All right, guys. In
order to keep the ground beef in the
diet, I've been mixing extra lean ground
beef with lean ground turkey. That way I
can keep the fat down and the flavor up.
And if you put enough seasoning in, you
really can't tell the difference. Now,
while his fast bulk had more room for
sweet treats, this time Dean had to get
creative.
>> So, I came up with a snack that's kind
of like a chocolate peanut butter frozen
yogurt snack.
And here it is.
M. Really good. Kind of tastes like a
Reese's peanut butter cup but with some
banana. And while I was worried Dean's
energy might take a hit, he seems to be
training just as hard with his new
workout buddy.
>> So, I got my new roommate and it's
actually my brother and it's been really
nice having him around. We've been
working out together, hitting PRs
together, pushing each other in the gym.
Today, we're doing dips. I'm going to
try and beat my PR. One, two,
24. Get 25 24.
>> Not only that, but they started prepping
meals together and keeping each other
accountable. But to Dton and Cole,
sticking to their training is more than
just for building muscle.
>> I've been working out the last year and
a half. Before that, I was an addict for
10 years, living on the streets, getting
in trouble. Uh, pretty much weighed
nothing. Now look at me. after dealing
with the loss of my grandfather. It's
really got me thinking about family, how
uh me and my brother lost my parents at
a young age. I really haven't had my
brother in my life for about 10 years
due to his own struggles. So, I'm just
really happy that he's uh doing better
and he's going to be living here.
>> And while Dane was enjoying his time
training with Cole, his progress on the
scale was completely stable, which is
exactly what we want. But it was now
hard for him to tell if he was making
any actual progress. But research shows
that if you keep your exercises the same
week after week and your strength is
going up, especially in the 6 to 12 rep
range, that is a very strong sign that
you are building muscle regardless of
what the scale says. Now, we'll see if
that's actually true for Dayton. But
I'll be honest, main gaining is just not
for everyone. If you're already pretty
lean, say under 15% body fat for men or
25% for women, your body may not have
enough stored energy to reliably fuel
muscle growth, which can leave you
spinning your wheels. And if you're
underweight, like I was growing up,
you're not going to gain 20 lbs by main
gaining. But if you have enough body
fat, you're newer to training, or you've
just never trained or dieted properly,
main gaining can be a great alternative
to constantly cycling between bulking
and cutting. Which is why at the end of
the video, I'm going to showcase the
results from all three diets and explain
which one will work best for you based
on your body. And bro, you are a master
of maintaining your weight because your
weight is the exact same as it was 30
days ago. Before I show you the Dex
results, let's pop open the hood. Now,
keep in mind that Dane did all of this
with only dumbbells, a bench, and a
pull-up bar. And what he doesn't know is
I'm going to be surprising him with a
brand new gym setup to help him and his
brother continue the journey. But before
I surprise him, let's review the results
of his final diet. Starting with muscle
gains.
Dude,
look at this chest, man. Every time I
see it, it's just like ballooning up.
Holy. So, after 30 days of his
maintained diet, Dayton gained an
impressive 1.1 lbs of muscle. That's
only 15% less than his lean bulk and 37%
less than his fast bulk, leading to a
total of roughly 4.4 lb of muscle over
the whole 90 days. But what's
interesting is his strength gains during
each diet actually match quite well with
how much muscle he ended up building.
So, if you don't have access to fancy
scans, tracking your lifts is an easy
and pretty reliable way to assess your
gains. Now, as for fat gain, for the
first time in our experiment, rather
than gaining, he actually lost a bit of
fat. His waist tightened up and some of
his belly fat actually came off. Which
brings me to our final question. Based
on the results of all three diets, which
one worked best and is the approach I'm
going to actually recommend for Damon?
Well, while the fast bulk delivered the
most gains and he did enjoy the extra
food, it came with a disproportionate
amount of fat gain, which I know Dayton
would end up regretting. As for main
gaining, I was honestly surprised with
how much muscle he still built. But
since I know he felt the best with more
calories, and he does want to prioritize
building muscle before attempting to cut
to 12% body fat for the summer, the lean
bulk, it just makes the most sense for
now. But that's just my take for Dayton,
and it might very well be different for
you. So, I wanted to make this chart
right here to help guide your decision.
But just keep in mind that in all three
diets, Dayton still made tremendous
progress. So, I don't want you to
overthink it. Eating well and training
hard is what's going to drive most of
your gains. And as for which diet,
Dayton's decided to stick with a leaner
bulk. I think if we stick to that, I
don't get too much belly fat over the
next few months, then I can hit that 12%
easier. Won't feel like I'm giving up.
so much.
>> True. And to help Dane get there, it's
time to reveal the surprise that I
prepared for him and Cole.
>> Yo, you went overboard, dude.
>> I don't think you know what this thing
can do.
>> I don't. That's what I mean, dude. I
have no idea. I got you a barbell. I got
you weight blades. I have more weight
plates coming.
>> Crazy, bro.
>> How's your whole experience been?
>> Amazing. I mean, my whole life changed
for so many positive ways. just diet, my
energy, everything's just been overall
better. And it's thanks to you and your
app. It's just so nice to not have to
overthink. It's just it does all the
little things, the monotonous stuff that
no one wants to do. It just takes care
of all of that.
>> If you guys want to give the app a shot,
you can get two weeks free at
billscience.com or scan this QR code
right here. And if you guys want to try
out a full body workout plan that's all
done for you, then give this video a
watch