Do you need carbohydrates to build muscle?

Every now and then someone tells me they are going keto and still expecting to grow.

No rice. No noodles. No fruit. Just meat, oil, avocados, and the confidence of a man who has just listened to a Joe Rogan Podcast.

And every time, the same question comes back to me. Can you actually build muscle without carbs?

For years the honest answer was "probably not as well, but nobody has really tested it on people who know how to train."

Well, somebody ACTUALLY kinda did.

The study

In 2021, a team of Italian researchers published a study (link at end of article): It is the first proper look at a ketogenic diet in competitive natural bodybuilders.

Nineteen men. 

Average age 27. 

All had been training for at least five years.

All competing in tested natural categories, all screened for steroid use. This ran in the off season, so these guys were trying to GROW, not trying to get shredded for a stage.

They got split into two groups for eight weeks.

The keto group, nine men, ate under 50 g of carbs a day. About 44 g. That is roughly one bowl of rice for the entire day, and everything else came from fat. The normal diet group, ten men, got 55% of their calories from carbs. Around 488 g a day.

Here is the important bit. Both groups ate the same calories (about 3,500 a day) and both ate the same protein (2.5 g per kg of bodyweight, which is over 200 g a day for these men). The ONLY thing that changed was carbs versus fat.

And they actually checked. Blood ketones tested every single week. Drop out of ketosis and you were out of the study. Nobody dropped out.

So this is not the usual "I did keto for two weeks and cheated on Saturdays" situation. These men did it properly. Very steady.

These are their measured results

Bodyweight barely moved. Keto went down about 1%, normal diet went up about 2%. Neither was big enough to mean anything.

Keto won on fat loss. The keto group dropped from 9.86 kg of fat to 8.42 kg, and that was a real result. The normal group went from 10.60 kg to 9.70 kg, which was not (I will explain this later). Same calories, more fat gone. Point to keto.

Carbs won on muscle. The keto group added 0.56 kg of lean mass, which was too small to count as anything. The normal group added 2.23 kg. Coles notes summary, the guys eating rice got bigger. The guys on keto stayed the same size.

Strength was a draw. Both groups got stronger and there was no meaningful difference between them. Keto added 4.13% to bench and 3.62% to squat. The carb group added 3.75% and 6.40%. Everyone improved. Nobody got weaker on keto. Remember that, because this matters.

Now hold on before you go and throw your rice cooker down the chute

I promised you honest, so here is honest.

They measured body composition with a bioimpedance machine. It sends a small current through you and guesses how much muscle you have, mostly based on how much water you are holding.

Now think about what keto does.

Your muscles store carbohydrate as glycogen. Every gram of glycogen you store drags about three to four grams of water in with it. Go keto and your muscles empty out, losing 40 to 50% of that store, and all that water walks out the door with it.

Your muscle is a sponge. Squeeze the water out of a sponge and it looks smaller and weighs less. But it is still the SAME sponge.

The machine however, cannot tell the difference. It just sees less water and reports less muscle. So some of that gap between the two groups is almost certainly water, not actual tissue.

There is a second problem too. Bodyweight went in opposite directions. The keto group finished 0.88 kg lighter, the carb group 1.33 kg heavier, even though both were prescribed the same calories per kilo. Neither shift was big enough to count statistically, so I won’t claim the two groups inadvertently ended up in different energy balances. But the study cannot rule that out either, and a guy in a small caloric deficit will always build less than a guy in a small surplus. That would have nothing to do with carbs at all.

Nine men against ten, eight weeks, everyone on their own training programme. So not quite consistent. Like the Italians and their cars: Sorry, JDM car guy here. 

Small study. The researchers say so themselves (Still more than our local professor’s “study” of ONE).

So no, this is not exactly proof that carbs are magic.

Calm down.

The hormone part is the real story

This is where it gets interesting, and this is the bit I trust most, because blood went to an accredited lab instead of a body fat gadget.

In the keto group, testosterone dropped about 10% and IGF-1 dropped about 16%. IGF-1 is one of the main signals your body uses to tell muscle to grow. Both drops were real.

In the carb group? Neither hormone moved. At all.

The researchers think this is WHY growth was blunted, and it makes sense. Low carbs means low insulin. And as I have mentioned before, insulin is an anabolic hormone. It is not the villain. Turn that signal down and you turn muscle growth down with it.

But keto won some serious things too

I am not here to bash keto. Look at what else happened in that group over eight weeks.

Triglycerides down 17%. HDL, the good cholesterol, up. Total cholesterol down. Fasting blood sugar and insulin both down. Two inflammation markers, both down. BDNF, a brain protein tied to mood and memory, up nearly 26%. And resting metabolism did not slow down at all.

None of that happened in the carb group.

So if you are in your 40’s, carrying a bit too much round the middle, and your last blood test made your doctor pull a face? This is a genuinely useful list. Keto could be a legitimate tool. It is just not the tool for the job of getting bigger.

And please ah, low carb is not keto

This one drives me up the wall.

This study tested under 5% of daily calories from carbs, 5% verified by weekly blood tests. Under 50 g. That is a hard, medically monitored diet.

It says absolutely NOTHING about you “cutting down on my carbs”.

If you have quietly halved your rice at dinner, this research is not about you. You are not on a ketogenic diet. You are just eating slightly less rice.

Like I always say: WE LIVE IN SINGAPORE. Nobody is giving up their chicken rice or their laksa. And you do NOT have to. You can build muscle perfectly well while eating both.Please refer to my previous articles. 

What this actually means for you

Keto did not eat into their muscle. Eight weeks of near-zero carbs and these men kept everything they had. The researchers credit two things for that. They kept lifting heavy, and they kept protein very high. That is the lesson. Protein and training did the saving, not the carbs.

If you want to grow, keep your carbs. Nothing here makes carbs magic. It just says that dropping under 50 g a day while trying to build is fighting yourself for no real prize. I’ve written about this in the past too.

If you want to lean out and fix your bloodwork, keto is a real option. The health markers in this study were genuinely impressive. Just go in knowing what you are trading.

Protein is still the king. 2.5 g per kg is why nobody in that keto group shrank. Get your protein in and most macro arguments become noise. I’ve repeated this in almost all my articles. And I’ll continue to bang on this drum till it is heard!!!

And it is just one study on only nineteen men over just eight weeks. It adds a piece to the puzzle. It does not end the argument, and anybody telling you it does is trying to sell you something.

The honest bit

For most of you reading this, this whole carbs vs fat argument is really the LEAST important thing about your training.

For one - you are probably not a natural bodybuilding competitor eating 3,500 calories and 200 g of protein a day with five years of hard training behind you. 

The thing holding your progress back is almost certainly not your fat and carbohydrate ratio.

It is training hard.

It is eating enough protein.

It is showing up consistently long enough for it to add up.

I know the simplicity of it is unsexy and boring. 

But it is however the truth.

And I am not going to pretend a simple macro tweak will do the job that showing up does.

If you are in Singapore and you want help figuring out where your macros should actually sit for what you are trying to achieve, or if you want us to help you prioritise your actions for your goals: Drop us a message and book a complimentary consultation with one of the personal trainers at the PIT. No obligations. No hard sell. Just personal training that fits around your food, your schedule and your life.

See you at the PIT Singapore.

Read the full study here

https://www.mdpi.com/2072-6643/13/2/374

Author: Henson Irving, PIT Director