BCAAs: Do Branched-Chain Amino Acids Really Work? [Science Explains]

If you want to boost your figure and gym performance, then you’ve likely heard of BCAA pills and powders.

They’re claimed to help you reach your goals faster and easier, whether you want to build muscle, lose fat, or gain strength.

But do BCAA supplements live up to those claims? Or are they just another fad that has taken the fitness world by storm? In this article, you’ll discover the unbiased, evidence-based truth on BCAAs.

We’ll look at what science says about BCAAs so that you can make an informed decision on whether supplementing with them will benefit you. Let’s dive in!


BCAAs: What Are They and Why Should You Care?

Branched-chain amino acids – or BCAAs, in short – are a group of three essential amino acids: isoleucine, leucine, and valine.

Supplementing with these amino acids may aid muscle growth, support fat loss, and enhance athletic performance.

Here’s how that works:

In total, there are 20 amino acids that your body needs to grow and function properly.

These amino acids are the building blocks of protein. They’re naturally present in protein-containing foods, such as meat, fish, eggs, nuts, legumes, and so forth.

Now, among the 20 amino acids, there’s one that has the most potent effects on muscle growth and recovery: leucine.

You can see leucine as the rock star among amino acids. Contrary to the other guests (amino acids), leucine has VIP access into the club (your muscle cells).

And once leucine reaches a muscle cell, it’s potent at turning up the muscle-building party because it stimulates mTOR, the primary muscle hypertrophy pathway in the body.

That’s why leucine is the big player among acids, and why it receives a lot of attention.

Hence, in-vivo research on young rats found that leucine supplementation stimulates protein synthesis to an equal extent as a mixture of all amino acids.[1]

Exciting, right? However, leucine has one downside: individual supplementation with the compound can deplete levels of valine and isoleucine in your body.[2]

Depleted levels of these amino acids can, in turn, hamper your figure, health, and well-being in various ways, such as by impairing energy production and glucose uptake into your (muscle) cells.

The good news? There’s a solution to leucine’s flaw. If you take it together with valine and isoleucine, you’ll reap the benefits of leucine without suffering its downside.

That’s why leucine is generally consumed alongside valine and isoleucine. And if a supplement contains this mixture, it’s what we call a BCAA supplement.

Do BCAAs Aid Muscle Growth?

BCAA pills and powders are one of the most popular supplements among bodybuilders. But do they really help you beef up?

Well, supplement manufacturers often cite research to “show” that BCAAs are “scientifically proven” to reduce levels of exercise-induced muscle damage and support post-workout muscle growth.[3-4]

And while gym-goers are often seduced by such claims, BCAA manufacturers don’t tell you the full story because there are three huge flaws to the studies they cite:

First, the human research studies which “show” that BCAA supplementation is beneficial for muscle growth are done on subjects that didn’t consume enough protein.

For example, one study that’s often used to promote BCAA products was done on wrestlers that were in a calorie deficit.[5] (So, they consumed fewer calories each day than what they burned.)

In the study, the researchers found those who supplemented with BCAAs daily maintained more muscle and lost slightly more fat than the control group after nineteen days of dieting.

A home run for the BCAAs, right? Well, not really… because what’s usually not pointed out is that the subjects only consumed around 80 grams of protein per day.

And since the average weight of the participants was 150 pounds, that number is way too low to maintain muscle mass during a calorie deficit – especially for competitive athletes.

The supplementation group, however, enhanced their daily diet with 52 grams of BCAAs. That’s a hefty amount, and it’s the reason they maintained more muscle.

So, what the research actually shows is that supplementing with BCAAs will reduce the damage if you don’t get enough protein. If we look at it from such a perspective, the study outcome isn’t that exciting anymore.

Secondly, only rat studies show that BCAA supplementation benefits muscle growth when enough protein is already consumed. (There’s no such research on humans; at least not quality ones.)

Rat studies have limited relevance to humans for two reasons:[6]

  1. The regulation of muscle protein synthesis (muscle growth) differs in many regards between rats and humans.
  2. Skeletal muscle makes up a much smaller percentage of total body mass in rats compared to humans.

In other words, it’s not valid to assume that BCAAs support muscle growth in humans because it does so on rats.

Thirdly, BCAAs are naturally present in food. So, you can get the benefits of consuming these amino acids by consuming protein-containing foods. This is a lot cheaper and as effective.

In fact, BCAAs in food form may even be more effective, as found by research published in Nutrition and Metabolism.[7]

In the study, the scientists noted that whey protein enhanced muscle protein synthesis significantly more than an amino acid drink.

Here’s what to do:

Rather than ordering a shiny new bottle of BCAAs, get your daily needs of the amino acids through food. Not only will this benefit your gains, but also your wallet.

To get enough BCAAs, consume at least 1.6 grams of protein per kilogram of body weight per day. So, if you’re 75 kilos, that’s a minimum of 120 grams of the macronutrient.

If you consume this much protein daily, you’ll experience all the muscle-building benefits protein has to offer, as concluded by a 2018 meta-analysis published in the British Journal of Sports Medicine.[8]

“But Wait… I Read a Study Which Showed BCAAs Are Legit for Building Muscle…”

When BCAA manufacturers are challenged on the effectiveness of the compound, they often mention research done in 2009 by Jim Stoppani and his colleagues.[9]

In the study, experienced resistance-trained athletes took 14 grams of BCAAs each day and gained, on average, 4 kg more muscle mass than the placebo groups after just eight weeks.

Besides, those who took the BCAAs also dropped their body fat percentage from an average of 9% to 7%.

Holy hawtastic! Those are some mind-boggling results, aren’t they?

Well, if you don’t evaluate the actual research, such an outcome makes it look like BCAAs are the best thing since sliced bread. However, there are three flaws with this study.

First, Scivation, a supplement company that sells a BCAA product called Xtend, funded the research. (Huge red flag!)

Secondly, the study never progressed through peer review. In other words, its publication has never been accepted in a scientific journal. (There must be a reason for that!)

Thirdly, the BCAA supplement also contained five grams of glutamine and two grams of citrulline malate. This may have benefited the results of the supplementation group.

So, instead of relying on such a flawed study, it’s better to bet on unbiased, peer-reviewed research to determine whether BCAA supplementation can help you pack on powerful muscle.

And if we do that, we’ll see that BCAA supplements won’t speed up your gains under most circumstances if you get enough protein.

I mention “under most circumstances” because there’s one situation in which BCAA supplementation may be beneficial.

BCAAs While Working Out Fasted – An Exception to The Rule?

By now, it may seem that BCAAs are a waste of money when it comes to building muscle.

And while that’s true in general, there’s one situation in which consuming a BCAA supplement can be beneficial for muscle growth: If you work out fasted.

Why’s that? Because if you exercise in a fasted state, muscle breakdown is increased. The reason is that your body uses more amino acids found in tissues such as muscle mass to produce energy.[10]

Now, if you take BCAAs before a fasted workout, you may slightly prevent this loss since leucine reduces muscle protein breakdown.[11]

Sure, you can get the same muscle-sparing benefits from consuming protein-rich food pre-workout. However, if you prefer to work out fasted, BCAAs can be beneficial.

Here’s what to do:

If you work out fasted, take 10 grams of BCAAs between 5 and 15 minutes before your session.

Do BCAAs Boost Weight and Fat Loss?

While aiding muscle growth is the main selling point of BCAA supplement manufacturers, this amino acid mixture is often also claimed to support fat loss. But do BCAAs really help you get lean?

Well, observational studies research show that an increased BCAA intake through diet is linked to a lower body weight.[12]

Those who consume, on average, 15 grams of BCAAs a day through food have up to a 30% reduced risk of becoming overweight or obese compared to those who consume an average of 12 grams a day.

Cool, right? Based on such data, it seems that BCAAs help you with obtaining and maintaining a shredded-to-the-bone figure.

But there’s a problem with relying on this data: those who consumed fewer BCAAs in the study also ingested around 20 fewer grams of protein per day.

And it’s well-documented that getting enough protein can aid weight loss because your food reward system has a strong appetite for the macronutrient.[13]

Hence, protein is so satiating that an increased intake of it tends to pair with an automatic drop in calorie consumption.[14]

And that’s likely why those who consume more BCAAs through diet have a reduced risk of becoming overweight or obese… they consume fewer calories.

But how about some actual data? Is there research that compares consuming BCAAs on weight and fat loss to not consuming the compound?

The answer is yes!

Research published in Journal of the International Society of Sports Nutrition looked at how 8 weeks of resistance training combined with BCAA supplementation influences body composition.[15]

The participants strength-trained for four days each week and either took nine grams of BCAAs around their workouts or a placebo.

The result?

There was no significant difference in weight and fat loss between the BCAA supplementation group and those who received a placebo.

In other words, if you want to rid yourself of excess pounds, there’s no need to stock up on BCAA pills and powders. Instead…

Here’s what to do:

Rather than supplementing with BCAAs, focus on the fat loss fundamentals that are proven to work.

The main one is being in a calorie deficit. So, consume fewer calories than you burn.

Besides, a few other important action-steps to nail down are consuming enough protein, staying hydrated, getting enough sleep, and following a sound exercise plan.

BCAA Supplementation May Enhance Athletic Performance

If you want to maximize your gym performance, then consuming BCAAs before your workout may help as this can reduce mental and physical fatigue.

For example, one study in which participants did a cycling test under heat exposure found that those who consumed the BCAA drink cycled, on average, for 12% longer than those who received a placebo.[16]

And another study found that that BCAA supplementation increased resistance to fatigue by 17% compared to a placebo.[17]

Not bad!

While there are different reasons why BCAAs can aid performance, one of the main ones is that your muscles use BCAAs during exercise. This causes levels of BCAAs in your blood to decrease.

Now, when blood BCAA levels drop, tryptophan levels in your brain rise.[18]

Tryptophan is a precursor of serotonin, a brain chemical that increases fatigue during exercise.[19-21]

However, if you consume BCAAs before your workout, tryptophan levels won’t drop as severely, and thus you’ll experience less fatigue.

Pretty cool, right? But here’s the catch…

You’ll only experience the performance-enhancing benefits of BCAAs if you don’t get enough of the amino acids through your diet.

If you already get enough BCAAs (which you do by consuming enough protein), then BCAA supplementation won’t further enhance your performance.[22]

Here’s what to do:

Don’t spend your hard-earned money on BCAA supplements in the hopes of boosting your gym performance.

Instead, cook yourself a steak or gulp down a protein shake before your workout. You’ll receive all the performance-enhancing benefits of BCAAs without emptying your wallet.

The Bottom Line on BCAAs

BCAAs are one of the most commonly used supplements among athletes. And while this compound is often claimed to help you build muscle, lose fat, and enhance your athletic performance, here’s the truth:

Unless you don’t get enough BCAAs through your diet or you work out on an empty stomach, supplementing with the amino acids won’t help you achieve your goals faster or easier.

Instead, if you already have your diet in check, the only thing that BCAA supplementation achieves is separating you from your hard-earned money.

So, instead of ordering another shiny tube of BCAAs, focus on getting enough protein instead. Do this by consuming at least 1.6 grams of protein per kilogram of body weight each day.


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3. Howatson, G., Hoad, M., Goodall, S., Tallent, J., Bell, P. G., & French, D. N. (2012). Exercise-induced muscle damage is reduced in resistance-trained males by branched chain amino acids: A randomized, double-blind, placebo controlled study. Journal of the International Society of Sports Nutrition, 9, 20.

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10. Pitkanen, H. T., Nykanen, T., Knuutinen, J., Lahti, K., Keinanen, O., Alen, M., . . . Mero, A. A. (2003). Free amino acid pool and muscle protein balance after resistance exercise. Medicine and Science in Sports and Exercise, 35(5), 784-92.

11. Mirza, K. A., Pereira, S. L., Voss, A. C., & Tisdale, M. J. (2014). Comparison of the anticatabolic effects of leucine and Ca-β-hydroxy-β-methylbutyrate in experimental models of cancer cachexia. Nutrition, 30(7-8), 807-13.

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18. Shimomura, Y., Murakami, T., Nakai, N., Nagasaki, M., & Harris, R. A. (2014). Exercise promotes BCAA catabolism: Effects of BCAA supplementation on skeletal muscle during exercise. Journal of Nutrition, 134(6), 1583-1587.

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22. Portier, H., Chatard, J. C., Filaire, E., Jaunet-Devienne, M. F., Robert, A., & Guezennec, C. Y. (2008). Effects of branched-chain amino acids supplementation on physiological and psychological performance during an offshore sailing race. European Journal of Applied Physiology, 104(5), 787-94.