Training Fasted? Consider Whey Protein Instead of BCAAs

Is it better to take Branched-chain amino acids (BCAAs) or whey protein when training fasted? Though the difference in outcome is likely small, it is exactly this kind of question that clients pay me to know and advise them on.

If you do your weight training fasted (in the morning without having eaten anything prior), it is advisable to take either a scoop of whey protein or BCAAs prior to training to minimize muscle breakdown.

Up until the end of last year, I recommended BCAA supplementation to clients who trained fasted. However, after a conversation with sports nutritionist and researcher Alan Aragon, I decided to change the recommendations I give to clients to favor whey instead.

This article explains my reasoning for this and the protocols I recommend for both the whey and BCAA supplementation.

Note: I have updated the BCAA energy values since the original publication. The article reflects these changes. I’ve added a note at the end explaining the reason why.

Why Whey Protein May be Better Than BCAAs When Training Fasted

Many of my clients are high achievers with demanding jobs. The majority choose to train early in the morning before the working day zaps their energy and motivation to train. They do not have any time to consume (and start to digest) a meal before training, which leaves them without any amino acids (the building blocks of protein) in circulation in their bloodstream to prevent muscle breakdown

This is where BCAA supplementation comes in as a recommendation. As the most important amino acids for muscle building, a BCAA powder can be consumed easily before training and absorbed quickly.

Typically, people who choose to train fasted in the morning will consume a 20 g dose of BCAAs split before and after their workout, with those that train very early in the morning consuming an additional 10 g due to the longer time until their lunch. This part of Martin Berkhan’s ‘Leangains’ protocol for his clients that train in the morning which I chose to adopt for my clients myself.

As you can see from the client results, this has worked well. Very well. So, this is not a question of whether this ‘works,’ it is merely a matter of whether whey consumption may be slightly more optimal.

BCAAs vs Whey: Comparing by Caloric Values

Contrary to what many products have on their labels, the free-form BCAA powders that we buy are not calorie free. They have a caloric value of 4.65 kcal/g, which means the typical 10 g serving has 46.5 calories. Geeky details here→1

So, why can manufacturers get away with not listing this on the packet you ask?

Because of a loophole in the FDA regulations. One states that supplement manufacturers can’t declare the protein content of a product when this only contains individual amino acids. Another allows supplement manufacturers to calculate the caloric content of their products using a number of methods, including the Atwater method, which involves adding up the calories from protein (4 kcal/g), carbs (4 kcal/g) and fats (9 kcal/g). Therefore, they aren’t required to list the calories. Shady shit, but to be expected from supplement manufacturers.

Though products vary, a standard commercial mix of whey concentrate and isolate (Optimum Nutrition Gold Standard Whey) has 120 kcal listed with 24 g protein per scoop.

Comparing the average BCAA formula with the average whey protein, we get the following:

10 g BCAA = 46.5 kcal = 0.37 scoop of whey = 9.3 g protein

20 g BCAA = 93 kcal = 0.77 scoop of whey = 18.6 g protein

30 g BCAA = 139.5 kcal = 1.16 scoop of whey = 27.9 g protein

The key difference is that with whey, we get the rest of the essential amino acids (EAAs) plus other anabolic/anti-catabolic co-factors that are missing in isolated BCAA, such as lactoferrin, beta-lactoglobulin, alpha-lactalbumin, glycomacropeptide, and immunoglobulins (hence its ability to support immune function). Whey also has antioxidant, antihypertensive, anti-tumor, hypolipidemic, antiviral, and antibacterial properties. You’d also be hitting the acute dosing ceiling for muscle protein synthesis with a full scoop.

In summary, taking whey protein costs less and you will get a marginally stronger anabolic response.

Fasted Training Supplementation Protocol Recommendations

Best option: Whey protein

Take a 25 g scoop of whey around 30 minutes prior to working out. Then take another 25 g scoop every 3 hours after that until your first meal of the day.

Count this against your protein targets for the day.

Second-best option: BCAAs

Take 10 g of BCAAs, (1 small scoop mixed in a 500 ml water bottle) 10 minutes before your weight lifting workouts. Take 10 g of BCAAs every 2-2.5 hours thereafter until your first meal of the day.

Because they have a caloric value, for every 10 g of BCAAs you consume, reduce your calorie intake by 46.5 kcal, by reducing your fat or carb intake (not your protein intake).

So, let’s say that you take 30 g of BCAAs, that’s ~140 kcal you need to remove from your diet. This can be achieved by reducing your carb intake by 35 g, fats by ~15 g, or a mix of both.

For more useful graphics, check out my Instagram.

Fasted Training and BCAA vs Whey FAQ

This section contains questions I anticipated, with the best I received from social media and email after the article’s publication.

Why should I not count BCAAs towards my protein intake target?

BCAAs are an incomplete protein, not as anabolic as whey alone. Therefore, I would not count the BCAAs against your protein targets for the day, but subtract them from the other macronutrients (carbs and fats).

Should I take whey concentrate, whey isolate, or hydrolyzed whey?

Whey concentrate and isolate will both digest in around 30 minutes. Isolate is a little more expensive but has fewer carbs in the mix, so it is worth consideration, especially when dieting.

Hydrolyzed whey is similar to whey isolate, but the protein has gone through a process called “enzymatic hydrolysis” which makes it faster to digest. It’s significantly more expensive, so unless you have less than 30 minutes between your alarm and the time you’re lifting something heavy, I don’t bother.

Can I take casein protein instead?

Whey and casein are both high-quality protein types (meaning they have an amino acid profile high in BCAAs). The difference is primarily in the rates of absorption, which will be significantly slower for the casein. As we want the amino acids to be in the bloodstream as quickly as possible when training fasted, whey protein is the best option.

Will this not ‘break’ my fast? I take BCAAs to not break my fast.

In both situations, you are no longer training fasted. (Yes, BCAAs have a caloric value but some manufacturers do not list it on the label. – This is something that caught me off guard for a long time also.)

If you want to train truly fasted, then you need to drink only water prior to training, which is simply not optimal. Why? Because what we are seeking to do here is minimize muscle breakdown during workouts (and promote growth, when possible).

Break your fast or break (down) your muscles. Choose wisely.

Given that the recommendations were originally part of Martin Berkhan’s protocol, what does he think of this?

I asked him to take a look at this before publishing to see if I had missed anything. He said it ‘looks good.’ I’m sure any updated thoughts from his original 2008-2010 articles will be included in his book.

What about BCAA supplementation outside the context of fasted training?

Completely fucking useless. Unless you’re not consuming an adequate amount of protein in your diet in the first place, but in which case, just eat more protein as it has more anabolic properties. Or just keep paying for this expensive, high-calorie, flavored drink that is costing you other food options in your daily caloric budget. It’s your choice, but make the decision an educated one.

It is at this point where I typically hear a rebuttal along the lines of the following: “But I feel so much more energized when I take BCAAs!”

That’s the caffeine in that BCAA product you are using (take another look at the label), some added arginine (or citrulline malate) causing your skin to tingle, or just a placebo effect – which I guess I’ve just killed for you.

What should I do if I have some leftover BCAA powder?

When it runs out, just switch. The difference is likely there, but marginal.

Do I have to supplement with whey or BCAAs for my fasted cardio workouts?

No. Fasted cardio won’t amount to the kind of stimulus where you’ll risk significant muscle breakdown, like with an intense resistance training workout.

What if I don’t want to train fasted?

That’s fine. I’m not telling you to and it’s not likely to give you a better result if all other variables are held constant.

However, if your workouts are currently compromised due to being rushed in the middle of the day, or you lack the energy after work in the evenings to train hard, this could be the answer as it has been for so many of my clients.

Did you update the article to change the caloric value of BCAAs?

Yes, twice.

I had previously listed the energy value of BCAA powders in a 2:1:1 mix as 6.38 kcal/g. I changed it to ~6 kcal/g, which is the metabolizable energy, not the gross energy. However, those figures applied to their protein-bound forms, so I have since adjusted that to 4.6 kcal, which is the energy value of the BCAAs we get in powder.


Thank you for reading. Questions welcomed in the comments.

– Andy


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  1. Leucine and isoleucine each have a gross energy of 6.52 kcal/g; valine has 5.96 kcal/g when protein bound. The metabolizable energy is slightly lower, 6.18 kcal/g and 5.55 kcal/g respectively.

    However, the free-form energy values in the BCAA powders we buy are 4.65 kcal/g, 4.65 kcal/g and 4.64 kcal/g for each of the three BCAAs respectively. Here’s the paper from where these numbers are derived.

About the Author

Andy Morgan

I am the founder of, this is my sincere effort to build the best nutrition and training guides on the internet. Some readers hire me to coach them, which I've been doing online, via email, for the last six years. If you're interested in individualized, one-on-one nutrition and training coaching to help you crush your physique goals, let's start the conversation.

8 Wordpress Comments

  1. Patrik Vidašič says:

    Hi Andy.

    What about HMB prior training? Whey and BCAA rise insulin very much, what is good after training but not before. What do you think?

    1. Andy Morgan says:

      At this point, with the research we have, HMB doesn’t appear to do very much for muscle growth. Though I know why you’re probably asking, the only really promising data (from Wilson and Lowery) appears to be fraudulent. This was discussed at length in the Podcast I did with Joseph Agu here, on the Podcast with Menno Henselmans here. You can see how ridiculous the data was visually here in that it out-performed testosterone injections (steroids), and you can read the full and scathing, unedited letter to the editor by 14 scientists, half of which whose names you have probably heard of here.

      Trust me, if there were something in it I wouldn’t keep it secret. I’d drink it, snort it, stuff it up my ass if I had to, but alas, no joy this time.

      Whey and BCAA rise insulin very much, what is good after training but not before.
      – What makes you say this?

  2. David says:

    Being 100% aminoacids, BCAA should be 4cal/g, not 6. Where did the latter figure come from? Just curious.

    1. Andy Morgan says:

      Hi David. The energy of the three BCAAs differ slightly.

      Leucine and isoleucine each have a gross energy of 6.52 kcal/g, valine has 5.96 kcal/g. However, the metabolizable energy is slightly lower, 6.18 kcal/g and 5.55 kcal/g respectively.

      This brings the average to 5.97 kcal/g when in a 2:2:1 ratio, as most BCAA supplement formulas are. I rounded this to 6 kcal/g.

      You’ll see I have added some extra detail within the text that can be activated by clicking the three little dots in a grey box. This was not obvious so I have highlighted them in red now.

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