Should You Take BCAAs Before Fasted Cardio?

Should you take BCAAs before fasted cardio?

If you’ve ever read a muscle building magazine, you’ll have seen this advice:

“Drink BCAAs before fasted cardio to prevent muscle breakdown.”

– every fitness magazine, ever.

But they’re wrong.

Now, before anybody gets all internet ragey on me, allow me to explain why you should not take BCAAs before fasted cardio…

fasted cardio bcaa myth

What Are BCAAs?

BCAAs is short for branched chain amino acids.

These little warriors are often called “the building blocks of muscle” because without them no muscle could be built at all.

The three BCAAs are leucine, isoleucine, and valine.

When we eat any protein, our body begins the process of breaking down that protein to draw out the these crucial little building blocks in order to feed our hungry muscles. This allows them to repair, and grow a little bit stronger for next time we smash them.

Supplementing with BCAAs directly (as opposed to just eating protein), rules out the need for the body to break anything down first.

should you take bcaas before fasted cardio

Should You Take BCAAs Before Fasted Cardio?

I have huge two issues with the old BCAA fasted cardio belief.

  1. To be concerned about “losing muscle”, you’d need to be tackling the workout regime of a f**king Olympian.
  2. BCAAs contain calories, therefore you are not performing fasted cardio.

Yep. That second point.

How did nobody spot that?

It’s largely because supplement companies claim that BCAAs have no calories on their nutrition labels, fooling people to believe that they can consume them without breaking a fast. However, as explained in this recent post, the reason it says no calories is because of a food industry regulation that states amino acids in their free form state cannot have a calorie content listed. It’s a bulls**t rule, but your BCAAs do contain calories.

So if our goal is to perform fasted cardio for fat loss, we’d be aborting that mission the moment we drank those BCAAs.

It’s an issue that runs deep in the fitness world, with many “experts” claiming you can buy a BCAA product and “sip on them all day long!”

(Please conveniently ignore the fact they also happen to own their own supplement line…)

A gram of BCAAs contains about 4.6 calories, which is slightly more than a complete protein. Which means that 20 grams of BCAAs (the usual serving we use) actually provides around 92 calories. (1)

should you use bcaas before fasted cardio

Should You Ditch Fasted Cardio Altogether?

Here’s the thing…

Everyone using BCAAs before fasted cardio is not actually performing fasted cardio. We know this by looking at the information above. But many people have still been getting great results.

Which begs the question, is fasted cardio even worth it?

I’ve never really been a fan.

I’m not going to bash it. You will still burn calories if you train in a fully fasted state, and you will still drop body fat if you are consistent in your efforts. Here’s a great article on that. It’s also a good way to start the day, because you put yourself into a calorie deficit from the get-go. (2)

But it comes with drawbacks…

The type of cardio you perform is one example.

Being fasted won’t affect you too much if you’re going for a brisk walk, but if you want to perform high intensity interval training you’ll notice a significant dip in max power output (and, therefore, potential total calorie burn from the workout itself) when compared to performing that kind of cardio in a fed state.

A 2010 study published in Medicine & Science compared the effects of two groups of participants training in either a fasted or fed state (pre workout whey protein). They noticed that the group who consumed protein experienced greater fat oxidation both during and after the workout was complete. (3)

Twelve months later, a second study confirmed these findings when they discovered once again that participants who consumed protein before training burned fat at an accelerated rate both during and after exercise. In fact, they were still ahead of the fasted group a full 24 hours later! (4)

So most of my athletes choose to perform morning cardio after the consumption of 20 grams of protein to unlock these results.

That being said, fasted cardio will still burn fat and many people do prefer it, so fill your boots.

But there’s one thing we can all agree on. The question “Should you take BCAAs before fasted cardio?” makes no sense at all.

Either take BCAAs and perform fed cardio, or don’t take anything and perform fasted cardio.

Make sense? If you enjoyed reading my take on the fasted cardio BCAA myth be sure to hop on my free email list down below, you’ll get bi-weekly tips straight outta my gym.


  1. May, M. E., et al. Energy content of diets of variable amino acid composition. Am J Clin Nutr. (1990)
  2. Gonzalez, J. T., et al. Breakfast and exercise contingently affect postprandial metabolism and energy balance in physically active males. Br J Nutr. (2013)
  3. Hackney, K. J., et al. Timing protein intake increases energy expenditure 24 h after resistance training. Int J Sport Nutr Exerc Metab. (2011)
  4. 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)

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