What Are Branched-Chain Amino Acids?

“TRUST ME, BRO. This will help you build muscle faster.” –zit faced gym-rat at your local supplement store.

  • Do BCAA’s really work or are they a scam?
  • What is the difference between EAA and BCAA?

Let’s see what the science and the evidence has to say….

What are BCAA’s? “Branched-chain amino acids (BCAAs) are essential nutrients. They are proteins found in food. Your muscles "burn" these amino acids for energy. The names of the specific amino acids that make up the branched-chain amino acids are leucine, isoleucine, and valine. The term branched-chain simply refers to their chemical structure.”[1] Leucine has been shown to have the most anabolic impact of the three aminos.

BCAA in and of themselves are essential for body composition no matter how they are sourced; complete protein sources like meats, fish, eggs, and some plants contain these aminos, which means the foundation of a healthy, lean, muscular physique should be dietary consumption through whole food sources. Research shows the recommended daily allowance (RDA) is insufficient to maximize muscle protein synthesis (MPS) in comparison to consuming a 1:1 protein-to-bodyweight ratio.[2] For example, as a rule of thumb, an athlete weighing 200 lbs would be wise to consume 200g of protein per day to maximize MPS.[3] Note that a well-executed ketogenic diet and/or intermittent fasting protocol lessens the requirements of protein due to the anti-catabolic nature of ketones present in a Calorie deficit, as shown in my own personal experience and professional natural ketogenic bodybuilders such as Robert Orion Sikes.[4]

Leucine, isoleucine, and valine are the three primary amino acids used for fuel to in resistance training. Amino acids are oxidized for energy along with ATP, glucose, your creatine phosphate system, fat stores (if you are in a Caloric deficit).[5]

Supplementing BCAA, particularly those with a 2:1:1 leucine-isoleucine-valine ratio, has grown in popularity as they have been proven to stimulate mTOR (mechanistic target of rapamycin), a primary controller of cell growth and proliferation. This signals muscle tissue cells to:

  1. Increase working capacity.
  2. Produce ATP (energy).
  3. Promote cellular regeneration, growth & repair.[6]

mTOR stimulation is the first thing that needs to happen for muscle building to take place; it’s like the foreman of a CONSTRUCTION CREW. They haven’t started working yet, but the command has been given to begin construction. Ingesting BCAA alone without any food will stimulate mTOR by itself as shown in a 2017 study following weight training: “We conclude that ingesting BCAAs alone increases the post-exercise stimulation of myofibrillar-MPS and phosphorylation status mTORC1 signaling.”[7]

But what happens after the foreman gives the command to begin construction? They need materials. On a job site, this includes lumber, rebar, cement, nails, etc. In your body, this includes all of the other essential amino acids (EAA). There are 20 total amino acids that are oxidized during physical exercise, and your body will pick and choose which ones to use depending on your exercises, intensity, and workout duration.[8] The three branched chain amino acids are like having the first few 2x4’s to get to work with…. But what about everything else?

That would be quite a disaster if the crew started working without everything they needed…. Labor costs would skyrocket as workers will be running back-and-forth to Home Depot to get what they need. The same thing happens in your body when mTOR is stimulated without the rest of the nutrition you need to recover.

You’re probably wondering, “Is it ever practical to ingest BCAA alone mid-workout as many athletes practice?” Science responds with a firm “NO.” Not only does BCAA ingestion alone not improve recovery, but it can also set back your progress in the same way the construction crew was set back due to poor planning. Ingesting BCAA in a relatively-fasted state mid-workout will trick your body into thinking it’s being fed, causing you to lose many of the performance benefits of your workout, when your body is producing testosterone, growth hormone, and other hormones crucial to your goals. This confusion is unnecessary, which is why it’s generally optimal to wait 30-60 minutes post-workout to consume protein.

Now you’re likely wondering if there is any use at all to supplement BCAA alone! Because BCAA are oxidized by the muscles, and not by the liver like food, they’re not digested in the same way as food.[9] This is good news for those of us who prefer to train fasted but want to squeeze in a small meal before training, don’t have time to eat a large meal of 30+g of protein, or for whatever reason don’t want to stress your digestive system with a meal and would like to maintain “relatively-fasted.” Perhaps you are following a ketogenic diet with a protein requirement that is less than the general 1:1 rule generally practiced among bodybuilding athletes in an attempt to maximize the benefits of becoming and remaining fat-adapted (difficult to do with a high consumption of dietary protein). Here would be a reasonable opportunity to supplement 5g of BCAA.

For this reason, there is a benefit to consuming dietary BCAA with a small meal that does contain all of the amino acids necessary for MPS to occur.

So why do many coaches and nutritionists advocate for EAA supplementation? First of all, let’s look at what EAA actually are. Of the 20 amino acids that comprise muscle protein, eleven (11) can be produced in the body, and nine (9) are considered to be “essential” because they cannot be produced by the body. During the catabolic state induced from intense exercise, especially during a Caloric deficit, your body will catabolize your lean muscle tissue to be oxidized as fuel needed from amino acids.[10]

A 2017 research study conducted by Dr. Robert Wolfe concludes: “A dietary supplement of BCAAs alone cannot support an increased rate of muscle protein synthesis. The availability of the other EAAs will rapidly become rate limiting for accelerated protein synthesis. Consistent with this perspective, the few studies in human subjects have reported decreases, rather than increases, in muscle protein synthesis after intake of BCAAs. We conclude that dietary BCAA supplements alone do not promote muscle anabolism.”[11] At the beginning of the conclusion he states, “A physiologically-significant increase in the rate of muscle protein synthesis requires adequate availability of all amino acid precursors.” Put simply, science shows that EAA supplementation mid/post workout does in fact improve recovery, whereas BCAA supplementation alone can actually IMPEDE recovery.

This must be why even professional-level natural bodybuilders who use very little supplementation, such as Robert Sikes, advocate EAA supplementation in certain circumstances: “You’ll likely be consuming all necessary amino acids from your diet along [on a contest prep], so there’s no need to waste money on expensive supplements that include undesirable filler ingredients and boatloads of sweeteners. The one caveat I have on amino acid supplementation is that I’ll often supplement with a quality EAA blend during the very tail-end of my prep.” –Robert Sikes[12]


  1. “Can BCAA hurt your progress?” YES; if ingested alone or post-workout this can cause your body to become confused because most of the necessary amino acids required for Muscle Protein Synthesis (MPS) are absent.
  2. “Do BCAA/EAA supplements contain Calories that should be tracked in a meal plan?” YES; research published in the American Journal of Clinical Nutrition shows approximate Caloric values of 4.7 Cal/g,[13] which is close enough to 4 Cal/g found in protein; therefore it’s practical to track it just like protein.
  3. “Can BCAA help you get the most out of a small meal with complete proteins?” YES.
  4. “If I’m on a tight budget, should BCAA supplementation be a priority?” NO! Most athletes new to training for muscle growth should start out with a good pre-workout and creatine as needed depending on their goals and physique preference.

In summary, your body requires a complete spectrum of 20 amino acids for MPS to occur. 9 of these are “essential” (EAA) meaning they must be included in your diet, and the 3 “branched-chain” amino acids (BCAA) are the most heavily used during weight training, and leucine is the most anabolic. However, despite how they are often used, BCAA alone simply does not serve any useful purpose in mid-workout training unless it is accompanied with the other 6 ESSENTIAL amino acids either by supplementation or with a post workout meal, though there can be a time and a place for strategic use if timed properly in diets lower in protein.


[1]Stuart, Annie. “Branch-Chain Amino Acids: Uses and Risks.” WebMD, WebMD, https://www.webmd.com/vitamins-and-supplements/branched-chain-amino-acids-uses-risks.

[2]Wilson, Cliff & Fitschen, Peter J. Bodybuilding: The Complete Contest Preparation Handbook, p. 55, FITbody and Physique LLC and Cliff Wilson © 2020.

[3]Kim, E, Dear, A, Ferguson, SL, Seo, D, and Bemben, MG. “Effects of 4 Weeks of Traditional Resistance Training vs. Superslow Strength Training on Early Phase Adaptations in Strength, Flexibility, and Aerobic Capacity in College-Aged Women.” J Strength Cond Res 25:3006-3013, 2011.

[4]Sikes, Robert. Ketogenic Bodybuilding: A Natural Athlete’s Guide to Competitive Savagery, p.101, Legacy Launch Pad Publishing, © 2022.

[5]Nelson, Tyarra. “#5 Myth-Busting the Science Behind BCAA’s.” The Bodybuilding Dieticians Podcast, Apple Podcasts. 08:08.

[6]Yazdi, Puya MD. “All About mTOR + Natural mTOR Inhibitors & Activators.” Selfhacked. June 18, 2021. https://selfhacked.com/blog/mtor-natural-mtor-inhibitors/

[7]Jackman SR, Witard OC, Philp A, Wallis GA, Baar K, Tipton KD. “Branched-Chain Amino Acid Ingestion Stimulates Muscle Myofibrillar Protein Synthesis following Resistance Exercise in Humans.” Front Physiol. 2017 Jun 7;8:390. doi: 10.3389/fphys.2017.00390. PMID: 28638350; PMCID: PMC5461297.

[8]Nelson, Tyarra. “#5 Myth-Busting the Science Behind BCAA’s.” The Bodybuilding Dieticians Podcast, Apple Podcasts. 09:05.

[9]“Do BCAAs Have Calories? Settling the Debate Once and for All.” Myoleanfitness.com. January 13, 2017. https://www.myoleanfitness.com/do-bcaas-have-calories/

[10]Wolfe RR. “Branched-chain Amino Acids and Muscle Protein Synthesis in Humans: Myth or Reality?” J Int Soc Sports Nutr. 2017;14:30. Published 2017 Aug 22. doi:10.1186/s12970-017-0184-9

[11]Wolfe RR. “Branched-chain Amino Acids and Muscle Protein Synthesis in Humans: Myth or Reality?” J Int Soc Sports Nutr. 2017;14:30. Published 2017 Aug 22. doi:10.1186/s12970-017-0184-9

[12]Sikes, Robert. Ketogenic Bodybuilding: A Natural Athlete’s Guide to Competitive Savagery, p.405, Legacy Launch Pad Publishing, © 2022.

[13]M E May, J O Hill, “Energy Content of Diets of Variable Amino Acid Composition,” The American Journal of Clinical Nutrition, Volume 52, Issue 5, November 1990, Pages 770–776, https://doi.org/10.1093/ajcn/52.5.770