Best BCAA for Fasted Cardio

By Performance Lab  |   | 

Do BCAAs enhance or disrupt intermittent fasting?

Branched-chain amino acids, or BCAAs, encompass a uniquely anabolic (muscle building) class of amino acids, making them particularly popular among bodybuilders.

But does that mean BCAAs only benefit bodybuilders?

Or can BCAAs also enhance the performance of, say, long-distance runners or any other class of aerobic exercisers?

More specifically, can BCAAs improve one’s fasted cardio results?

As the advantages of fasted cardio and fasted training (i.e., exercising on an empty stomach) become more widely well-known and understood, the question of combining fasted training with BCAAs has also been on the rise.

Key Point: While fasted training seems to improve fat loss and lean muscle gain results, exercising on an empty stomach also seems to increase the rate of protein breakdown.

Conversely, BCAAs seem to slow down the rate of protein breakdown...

...making the combination of fasted training and BCAA supplementation a potential match made in heaven.

But is that the only effect BCAAs have on fasted training?

Or does this benefit come at the cost of disrupting all the other metabolic health benefits of intermittent fasting and fasted training?

In this article, we cover:

  • the ins-and-outs of intermittent fasting
  • fasted training
  • branched-chain amino acids to better determine the advantages of combining fasted training with BCAAs.

All you need to do is keep reading!

The Beginner’s Guide on Fasting with BCAAs

Simply put, fasting involves abstaining from all foods and drinks, with exception to a few fasting-friendly drinks such as water, black coffee, tea, and apple cider vinegar.

And intermittent fasting involves intermittently abstaining from all foods and drinks, etc. by splitting the diet into scheduled increments of “fasting” and “feeding.”

This means saving your post-workout protein shake for the “feeding” portion of your intermittent fasting schedule.

However, that means ending your fast after your workout, if you’re hoping to enjoy the benefits of fasted training—i.e., exercising on an empty stomach.

But, of course, exercising on a completely empty stomach is a difficult strategy for optimizing your exercise performance.

Which is why supplementing Branched-Chain Amino Acids (BCAAs), the basic building blocks of protein, may help you extend your exercise endurance and net better fasted training results without totally derailing the benefits of your fast.

Though they don’t encompass all of the essential amino acids, branched-chain amino acids (BCAAs) include the three most anabolic (muscle building) amino acids:[1]

  • L-Leucine – the most important BCAA for muscle growth, L-leucine is an anabolic amino acid that promotes protein synthesis, muscle growth and repair.
  • L-Isoleucine – required for hemoglobin to assist red blood cells with the transportation of oxygen to muscle tissue, L-isoleucine is a key BCAA for tissue repair, muscle energy, and immune health.
  • L-Valine – required for protein synthesis, L-valine encourages muscle tissue growth and repair while also functioning as an integral source of muscle energy itself.

Due to BCAAs’ association with protein, which must be avoided during the “fast” state of intermittent fasting, many sports nutrition enthusiasts fear that BCAA supplementation may disrupt the benefits of intermittent fasting and fasted cardio.

Others, however, suggest that BCAAs are too simple in structure to impair the fasting state, and that there are significant fitness and health advantages to adding a BCAA stack to your intermittent fasting regimen.

To determine which of these claims are true, we need to first answer this question:

Does Intermittent Fasting (IF) Work?

The benefits of intermittent fasting (IF) are many, including better health outcomes related to overall metabolism, cholesterol, blood pressure, glucose, insulin, and many other biochemical markers.[2]

When combined with exercise, intermittent fasting can be an incredibly effective strategy for promoting lean muscle gains and fat loss.

A plate with a clock on top to signify intermittent fasting

How Does Intermittent Fasting Work?

Essentially, intermittent fasting works by mimicking the feeding patterns of a food-scarce environment. Though many of us live in food-rich environments, where on every street corner there’s a diner or fast-food drive-thru, our bodies remain primed for the wilderness.

And in the wilderness, constant eating is rare and unnatural, and, thus, constant eating may drastically impair our metabolic performance.

By temporarily forcing the body into a fasted state, intermittent fasting allows the body to metabolically “reset,” acting as a sort of stress test to ensure the body’s systems are all in working order.

Intermittent fasting does not require calorie restrictions or special meal plans to work. Intermittent fasting is a matter of scheduling, not dieting.

Because intermittent fasting is strictly focused on the benefits of fasting, you’re not necessarily required to reduce your daily calorie count or remove certain foods from your diet for intermittent fasting to work.

Naturally, your diet will alter under intermittent fasting conditions. However, diet aside, intermittent fasting regimens are hypothesized to influence metabolic regulation via effects on:[3]

  • Circadian Rhythm – your internal biological clock
  • Intestinal Microbiota – beneficial gut bacteria and enzymes
  • Lifestyle Behaviors – diet, sleep, and exercise activity tend to alter with a scheduled fasting routine

And more. Most notably, intermittent fasting’s effects on energy expenditure—namely on ketosis, a metabolic state that encourages the use of stored fat as energy fuel—have contributed to the trend of fasted training as a health and fitness strategy.

The Metabolic Benefits of Fasted Cardio

Typically, the goal of fasted cardio is to increase fat burning and improve your body composition.

After all, without any food fuel readily available, the body will have to resort to stored energy (i.e., fat) to do all the amazing things that the body does, right?

That’s the idea, at least!
However, thanks to clinical research, this is more than just an idea.

On the potential metabolic benefits of fasted cardio, two systematic reviews stand out:

Systematic Review #1

Conducted in 2016, this study aimed to verify the effect of aerobic exercise performed in the fasted vs. fed states on fat and carbohydrate metabolism in adults, a total of 273 participants.

Based on outcomes measuring fat oxidation, glucose, and insulin, the researchers concluded that “aerobic exercise performance in the fasted state induces higher fat oxidation than exercise performed in the fed state.”[4]

Systematic Review #2

Conducted in 2018, this review aimed to determine the effects of fasting vs. pre-exercise feeding on aerobic and anaerobic exercise performance, as well as post-exercise metabolic adaptations.

In total, 46 studies were analyzed by the researchers, whose findings supported the hypothesis that fasting vs. feeding divergently influence exercise performance and metabolism. Their conclusion: “Pre-exercise feeding bolsters prolonged aerobic performance, while seminal evidence highlights potential beneficial metabolic adaptations that fasted exercise may induce in peripheral tissues.”[5]

When is the Best Time to Exercise on an Empty Stomach?

Exercising first thing in the morning, prior to breakfast, is a popular fasted cardio strategy for a couple reasons:

  1. Daytime discomfort of fasting is subjectively short-lived.
  2. Morning exercise kickstarts the body’s fat burning metabolism early, lowering the likelihood of overeating throughout the day.[6]

This means fasting throughout the evening and night, exercising on an empty stomach in the morning, then breaking the fast with breakfast, as originally intended by the word “breakfast.”

However, as with any intermittent fasting schedule, one issue here remains: Is it okay to supplement BCAAs during the fast without breaking the fast too early?

The Advantages of BCAAs While Fasting

The effectiveness of BCAAs is well-known and well-documented. There’s a reason why BCAAs are one of the most popular workout supplements: They work.

More importantly, BCAAs work under fasting conditions as well.
Simply put, the body needs BCAAs to build muscle tissue.

And given that exercise promotes BCAA catabolism (breakdown),[7] it’s fair to say that the exercising body really, really needs BCAAs to build muscle. BCAA supplementation helps meet that need, whether you take it pre-workout, intra-workout, or post-workout.

According to clinical research, BCAA supplementation may improve exercise and muscle performance by boosting:[8-11]

  • Protein Synthesis – by stimulating IGF-1 growth hormone activity
  • Insulin Activity – which enhances uptake of amino acids in muscle tissue
  • Cellular ATP Energy – after glycogen stores have been depleted
  • Exercise Endurance – by impairing fatigue-inducing brain activity
  • Muscle Protection – against the catabolic effects of exercise
  • Glutamine Levels – which in turn support the immune system

BCAA supplementation may help reduce muscle damages associated with endurance exercise.[12]

Though weight loss via fat loss is a commonly desired consequence of fasted cardio, muscle loss is not.

Because branched-chain amino acids convert to protein—not fat—and promote anabolic muscle gains, BCAA supplements may help boost your fasted training results without impairing your fat burns.

Quite the opposite, in fact, considering how an increase in lean muscle mass contributes to a general increase in your fat-burning metabolism.

Do BCAAs Kick you out of Ketosis?

Because BCAAs have a stimulatory effect on insulin activity, many sports nutrient enthusiasts worry that BCAA supplementation may override the ketosis-related benefits of intermittent fasting.

However, some research suggests that BCAAs might act synergistically with a ketogenic diet:[13]

One small pilot prospective study observed the effects of BCAA supplementation as additional therapy to the ketogenic diet on children with epilepsy.

The researchers noted no reduction in ketosis with BCAA supplementation, despite a change in fat-to-protein ratio, leading to the suggestion that “branched chain amino acids may increase the effectiveness of the ketogenic diet and the diet could be more easily tolerated by the patients because of the change in the ratio of fat to protein.”

What to Look for in a BCAA Supplement

Aside from supplying the three branched-chain amino acids (L-leucine, L-isoleucine, and L-valine), the criteria for the Best BCAA for Fasted Cardio include:

Muscle-Optimized 2:1:1 Ratio

Because L-leucine is generally considered to be the most anabolic of the three BCAAs, many supplement manufacturers overemphasize L-leucine in their formulas, loading up on the amino at 4:1:1 (or even up to 10:1:1) ratios of L-leucine to L-isoleucine to L-valine.

The problem with this: As BCAA ratios go up, research and safety date go down.

Mirroring the 2:1:1 ratio of L-leucine to L-isoleucine to L-valine naturally found in muscle tissue, 2:1:1-ratioed BCAA supplements are not only organically optimized for muscle delivery but they are also backed by the most clinical research.

Don’t be fooled by BCAA stacks that advertise having an exceptionally anabolic amount of L-leucine. The best BCAA ratio is the muscle-optimized 2:1:1 ratio.

Easy-to-Absorb Ingredient Forms

While having the correct amino acids at the correctly ratioed dosages is a key criterion for identifying the best BCAA for fasted cardio, ingredient quality is arguably just as important as ingredient quantity.

After all, as a time-sensitive intra-workout supplement, the chosen BCAA ingredient forms must be potent and absorbable enough to deliver their muscle-nourishing benefits during the immediate workout to work properly. Otherwise, you’ll miss out on the acute performance enhancing benefits of BCAAs, resulting in a lower-intensity workout.

Pure, bioavailable, nature-identical BCAAs are always the superior option over cheap, synthetic BCAAs. This applies both to the quality of the BCAAs and to the quality of the formula delivering the BCAAs, meaning that any BCAA supplement that comes stuffed with artificial additives, unnatural dyes and colorants, messy preservatives, and GI-disruptive sweeteners isn’t worth your time (or money).

An effective BCAA stack is clean and all-natural, removing all unnecessary artificial additives and byproducts that might otherwise impair quick BCAA delivery and absorption into your exercising muscle tissues.

Simple “Non-Hybrid” Formula Design

The best BCAA supplement supplies a clean source of absorbable, bioavailable branched-chain amino acids …and that’s it.

No unnecessary ingredients, such as caffeine or any other stimulant energy boosters, to fulfill some “hybrid” marketing angle on the product label. While there are certainly many clever, creative ways to stack BCAAs with other performance enhancing ingredients, it’s best to include those other performance boosters as separate formulas.

Again, much of the success of a BCAA stack relies on its potency. Overstuffing too many ingredients that have nothing to do with promoting anabolic muscle gains are likely to only get in the way of a BCAA stack’s primary ingredients: the BCAAs.


The benefits of fasted training appeal to those looking to gain lean muscle mass while promoting fat loss. Yet, the downside to fasted training is undeniably annoying: fasted training may increase catabolism (muscle breakdown) more so than well-fed training.

Simply put, you exert all that self-control to maintain fasting conditions and you invest all that energy and effort in the gym only to make it easier to lose muscle mass.

While the two camps on BCAA and intermittent fasting remain polarly split on this point—BCAAs enhance intermittent fasting! BCAAs disrupt intermittent fasting!—the evidence seems to favor the advantages of BCAA supplementation over any supposed disadvantages to supplementing BCAAs while fasted training.

At the least, if increased muscle mass is a core goal of your fasted training and cardio strategy, an effective BCAA supplement is an effective optimization tool for getting the most out of your intermittent fasting efforts. Even for fat loss, research suggests that increasing your BCAA intake is the way to go.[14,15]

Either way, branched-chain amino acid supplementation is a great sports nutrition option for cardio exercisers and anaerobic bodybuilders alike.

Best Supplement Stack for Fasted Cardio

Though the question of supplementing BCAAs while intermittent fasting and/or fasted training is a controversial one, there are many health and fitness supplements that not only work under fasted conditions but may even improve your fasting results.

To create the Best Supplement Stack for Fasted Cardio, add the following formulas to your fitness routine:

Performance Lab® MCT

A bottle of Performance Lab MCT Oil

The world’s cleanest MCT oil for fast-acting brain energy, fasted training, metabolic performance, and overall health and fitness.

Taken daily, Performance Lab® MCT offers a fast-acting, long-lasting source of energy to keep the brain fueled through fasting conditions without disrupting the fast.

Quite the opposite, in fact: by converting to ketones, a fat-sourced energy fuel substitute for glucose, MCT oils encourage fat-burning ketosis for ATP energy production, thereby enhancing the metabolic benefits of intermittent fasting.

And by providing both C8 (the most keto-active MCT) and C10 (a mitochondrial protecting MCT), Performance Lab® MCT targets a wider range of energy benefits than your standard C8-only MCT oil supplement.

  • Supplement Facts: C8/C10 MCT (Medium Chain Triglycerides) Oil from 100% Organic Coconuts

To get the best deal on Performance Lab® MCT, click here.

Performance Lab® Energy

A bottle of Performance Lab Energy

Ultramodern stim-free energizer for advanced mitochondrial support, cell energy enhancement, and a daily boost on long-term vitality.

Though caffeine is a favorite energy booster among fasted cardio trainers, particularly for the stim’s appetite suppressant effects, Performance Lab® Energy’s stim-free formula design offers a more advanced energy boosting complex that naturally promotes the body’s natural energy output biomechanisms.

By promoting and protecting mitochondrial cell energy output, Performance Lab® Energy’s antioxidant complex assists with daily vitality, peak athletic performance, cognitive clarity, fat metabolism, and many more long-range health benefits.

  • Supplement Facts: Acetyl L-Carnitine (from Acetyl L-Carnitine HCL), Microencapsulated Bio-Enhanced® R-Lipoic Acid, MicroActive® Q10 (Coenzyme Q10), BioPQQ® (Pyrroloquinoline quinone [PQQ]), BioPerine® Black Pepper Extract (Piper nigrum) (fruit) (95% piperine)

To get the best deal on Performance Lab® Energy, click here.


  1. Holeček M. Branched-chain amino acids in health and disease: metabolism, alterations in blood plasma, and as supplements. Nutr Metab (Lond). 2018; 15: 33.
  2. Ganesan K et al. Intermittent Fasting: The Choice for a Healthier Lifestyle. Cureus. 2018 Jul; 10(7): e2947.
  3. Patterson RE et al. Intermittent Fasting and Human Metabolic Health. J Acad Nutr Diet. 2015 Aug; 115(8): 1203-1212.
  4. Vieira AF et al. Effects of aerobic exercise performed in fasted v. fed state on fat and carbohydrate metabolism in adults: a systematic review and meta-analysis. Br J Nutr. 2016 Oct; 116(7): 1153-1164.
  5. Aird TP et al. Effects of fasted vs fed-state exercise on performance and post-exercise metabolism: A systematic review and meta-analysis. Scand J Med Sci Sports. 2018 May; 28(5): 1476-1493.
  6. Bachman JL et al. Exercising in the Fasted State Reduced 24-Hour Energy Intake in Active Male Adults. J Nutr Metab. 2016; 2016: 1984198.
  7. Shimomura Y et al. Exercise Promotes BCAA Catabolism: Effects of BCAA Supplementation on Skeletal Muscle during Exercise. J Nutr. 2004 Jun; 134(6): 1583S-1587S.
  8. Greer BK et al. Branched-chain amino acid supplementation and indicators of muscle damage after endurance exercise. Int J Sport Nutr Exerc Metab. 2007 Dec; 17(6): 595-607.
  9. Matsumoto K et al. Branched-chain amino acid supplementation attenuates muscle soreness, muscle damage and inflammation during an intensive training program. J Sports Med Phys Fitness. 2009 Dec; 49(4): 424-31.
  10. Jackman SR et al. Branched-chain amino acid ingestion can ameliorate soreness from eccentric exercise. Med Sci Sports Exerc. 2010 May; 42(5): 962-70.
  11. Zanetti M et al. Effects of branched-chain-enriched amino acids and insulin on forearm leucine kinetics. Clin Sci (Lond). 1999 Oct; 97(4): 437-48.
  12. Dong-Hee K et al. Effect of BCAA intake during endurance exercises on fatigue substances, muscle damage substances, and energy metabolism substances. J Exerc Nutrition Biochem. 2013 Dec; 17(4): 169-180.
  13. Evangeliou A et al. Branched chain amino acids as adjunctive therapy to ketogenic diet in epilepsy: pilot study and hypothesis. J Child Neurol. 2009 Oct; 24(10): 1268-72.
  14. Qin LQ et al. Higher Branched-Chain Amino Acid Intake is Associated with a Lower Prevalence of Being Overweight or Obese in Middle-Aged East Asian and Western Adults. J Nutr. 2011 Feb; 141(2): 249-254.
  15. Novin ZS et al. The Weight Loss Effects of Branched Chain Amino Acids and Vitamin B6: A Randomized Controlled Trial on Obese and Overweight Women. Int J Vitam Nutr Res. 2018 Feb; 88(1-2): 80-89.
[article-cta-inline category="bcaa-1"] [article-cta-sidebar category="bcaa-1"]