Should You Use BCAAs Before Fasted Cardio?

Should you use BCAAs before fasted cardio?

This is a piece of advice regularly cited in bodybuilding magazines and there are thousands of people around the world who do it every day.

But they’re wrong.

That’s right.


Now, before you internet rage all over me, allow me the opportunity to explain why I take this stance…

What Are BCAAs?

BCAA is short for branched chain amino acids.

These little bad boys are often called “the building blocks of muscle” because, well, they are. Without them, no lean muscle could be built!

The three BCAAs are leucine, isoleucine and valine.

When we eat protein, our body begins the process of breaking down the protein source to draw out these crucial little building blocks and feed our tired muscles so that they can repair, and grow stronger.

Supplementing with them directly simply rules out the need for our body break them down.

should you use bcaas before fasted cardio

So Should You USE BCAAs Before Fasted Cardio?

I have two problems with this training myth.

  1. You’d need to have an incredibly difficult training regimen to even have a legitimate right to worry about muscle loss.
  2. BCAAs contain calories, therefore your fasted cardio is not fasted at all.

Yep. That second point.

It’s like the moment you realize Bruce Willis is a ghost in The Sixth Sense.

Most BCAA supplements list themselves as having zero calories, fooling many fitness enthusiasts to presume they can drink BCAAs before fasted cardio without breaking their fast.

Some “experts” even proclaim you can “sip on them all day long!”

(Please ignore the fact that they happen to own a supplement line…)

However, in my recent article How Do BCAA Supplements Have Zero Calories I explained that this is due to current FDA regulations, which state that:

“Protein shall not be declared on labels of products that, other than ingredients added solely for technological reasons, contain only individual amino acids.”

They are not a miracle food.

They are not calorie-free.

One gram of leucine, isoleucine or valine (or a combination of all three) contains around 4.6 calories.

Which means that 20 grams of BCAAs provides you with around 92 calories.

Protein itself contains only 4 calories per gram, so how is it possible for BCAAs to contain 4.6? Well, that’s because in their free-form state they do not represent a complete protein source, forcing the calories-per-gram count slightly higher. (1)

Is Fasted Cardio Better Than Normal Cardio, Though?

I know…

World rocked…

But now that we know taking a BCAA supplement before fasted cardio means you have broken your fast and are therefore no longer performing fasted cardio, we have to ask ourselves whether we should be performing fasted cardio at all.

I mean, there are literally thousands of people around the world taking BCAAs before training and seeing results without even realizing that they’re not actually doing fasted cardio – so how do we know that results would improve if they were to ditch the pre workout BCAAs and go in purely fasted?

Well, there’s nothing really bad about fasted cardio.

You will burn calories and you will certainly drop body fat. Here’s a great article on that. (2)

It’s also a great way to start the day, by placing yourself into a calorie deficit almost immediately upon waking.

But there are drawbacks.

The type of cardio you perform will present the first obstacle.

If you are going for a brisk walk, then you shouldn’t expect any problems. But if you are performing high intensity interval training you’ll notice a significant dip in max effort levels (and therefore potential calorie burn) versus training in a fed state.

Many of my clients over the years have tried this for themselves, and noticed a feeling of “running on empty”, and being unable to hit the training intensity they’re accustomed to. As such most of them don’t do fasted cardio nowadays.

bcaa before fasted cardio

Actor Adam Baroni during an outdoor cardio session.

And then there’s the research…

A 2010 study published in Medicine & Science compared the effects of two groups of participants training in either a fasted state or having consumed pre workout protein.

They noticed that the group who consumed protein experienced greater fat oxidation both during and after the training was complete. (3)

Then, a 2011 study published in the International Journal of Sport and Nutrition and Exercise Metabolism confirmed these findings when participants in a different trial were found to be burning fat at an accelerated rate both during and after exercise.

In fact, they were still ahead almost 24 hours later. (4)

Here’s an article on that.

bcaa pre workout

Final Thoughts

It’s really your choice whether you’d like to do fasted cardio or not.

I consider it yesterday’s advice, particularly if you are training at a high intensity, but it’s your decision.

However, there is one thing we can definitely agree on – the question “Should You Use BCAAs Before Fasted Cardio?” makes no sense!

If you take BCAAs before fasted cardio, you are no longer doing fasted cardio.

If you truly want to train in a fasted state, you’d be better served by sticking to water.

Make sense? Good!

If you enjoyed my piece on ‘Should You Use BCAAs Before Fasted Cardio?’, drop a like on it to educate some gym buddies.

12 thoughts on “Should You Use BCAAs Before Fasted Cardio?

  1. I’ve legit been doing this for months and not knowing I’ve been breaking my fast thanks to no calories being listed on the back of the God damn tub. Thanks for the info.

  2. Good post. I agree, BCAA’s will certainly break your fast – although I didn’t know about the calorie listing thing.

  3. I’ve always wondered this!! Like, where do the calories suddenly come from if it’s consumed as whey protein?! Great post.

  4. Not being able to list calories on BCAA supplements needs sorting out ASAP. I always thought they were calorie free due to it actually saying ZERO CALORIES. It would be different if they simply didn’t list the calories, but they make an effort to say there is none. What a whack rule.

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