Should you take BCAAs before fasted cardio? Muscle building magazines often say yes, but today you’ll see why the fasted cardio BCAA myth is DEAD WRONG.

should you take bcaas before fasted cardio

Written by Russ Howe PTI, and most recently updated 1 day ago.

2 min read

Fitness magazines have long claimed that you should take BCAAs before fasted cardio, stating that they’ll increase energy and prevent muscle breakdown.

But here’s the thing…

This advice is DEAD WRONG.

The Fasted Cardio BCAA Myth

do bcaas contain calories

At this junction it’s only fair that I redirect some of you to my earlier article where I explained why fasted cardio is not better then regular cardio.

You see, I’m a big fan of fasted cardio, and I know lots of my readers are too, but many people hate it and only do it because they’ve been told it burns more fat, and we know that’s not the case. If that’s you, I recommend reading that article instead. (1, 2, 3)

Still here?


So if your goal is to perform fasted cardio, drinking BCAAs would be a bad idea because BCAA supplements contain calories; meaning you are no longer training in a fasted state. BCAA supplements often show 0 kcals on their nutrition labels but this is not true, it’s just that supplement industry law states that the calorie conent of individual amino acids does not need to be listed. Research shows that there are 4.6 calories in one gram of free-form amino acids, so a 30g serving of BCAAs would be 138 calories, and this would break your fast. (4)


  1. Gonzalez J. T., et al. Breakfast and exercise contingently affect postprandial metabolism and energy balance in physically active males. Br J Nutr (2013).
  2. Hackney K. J., et al. Timing protein intake increases energy expenditure 24 h after resistance training. Int J Sport Nutr Exerc Metab (2011).
  3. Paoli A., et al. Exercising fasting or fed to enhance fat loss? Influence of food intake on respiratory ratio and excess postexercise oxygen consumption after a bout of endurance training. Int J Sport Nutr Exerc Metab (2011).
  4. May M. E., et al. Energy content of diets of variable amino acid composition. Am J Clin Nutr (1990).

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I’m Russ. I’ve been a personal trainer since 2002, and I own

My job is to simplify fitness for my readers.

I send out free fitness tips to over 100,000 men and women every week, all in the same no-nonsense style as the article you’ve just read, so if you enjoyed reading it be sure to jump on my email list below.

One response to “Should You Take BCAAs Before Fasted Cardio?”

  1. Rob Delaney avatar
    Rob Delaney

    Russ you absolute bastard. Where were you 20 years ago when I first started buying Bcaa’s???????

    JK, love your work my man. Learned something new here today!

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