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

Hi, I'm Andy, co-author of 'The Muscle and Strength Pyramid' textbooks and founder of This site 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 full-time, online, for the last seven years. If you're interested in individualized, one-on-one coaching to help you crush your physique goals, let's start the conversation. (You can read more detailed bio here.)


  1. Aman says:

    Hey Andy! Bit confused about consumption of whey preworkout. Will it not negate the benefits of fasting(fat burning mostly) because obviously it will break the fast. I read where you said break muscle or break the fast. I’m somewhere around 15% as per your guidline I take whey 30 mins prior to workout and train at 8.30 then whey post workout and every 3 hours until I eat solid food around 2. If I don’t use whey pre and post and just break fast at 2pm, am I at risk of loosing too much muscle.
    Current goal is get down to around 6-7%. Thanks for all the info Andy

    1. Andy Morgan says:

      Will it not negate the benefits of fasting (fat burning mostly) because obviously, it will break the fast.
      – In this regard, morning fasting is overhyped. It won’t make a difference to total fat burned as long as the calorie balance is maintained throughout the day.

  2. Mike says:

    Hi, great article. Two questions: why the difference in time window between whey and BCAAs? Anything wrong with following the 2/2.5 hrs for whey?

    Also, what about HIIT? It’s very taxing, so I follow the whey protocol even though you said no need for cardio. Thanks!

    1. Andy Morgan says:

      Hi Mike,
      1. Different digestion rates (the BCAAs are free-form, protein that has already been broken down).
      2. If the kind of HIIT you’re doing leaves you sore, I could make a case for it.

  3. Patrick Norton says:

    Andy, thanks for this excellent and insightful article. I have a question based on this: I am one of those need-to-work-out-before-work guys, and I’m not looking to add bulk (yet) but to lose about 30 pounds first while strengthening up. I have read a number of articles championing BCAAs for the prevention of muscle loss during workouts while on a calorie deficit diet. Does your position include people who are looking to aggressively lose weight while adding muscle, or should I work first to meet my weight goal (including BCAAs) and then move to your strategy? Will whey protein also prevent my body from eating muscle mass to protect its beloved fat stores?

    1. Andy Morgan says:

      Whey is likely to be the best option, but if you have an aggressive deficit you’ll compromise what strength and muscle gains you can achieve while cutting and possibly lose muscle mass.

      The fastest way to your dream physique is not the one where the numbers move the fastest. Set your weight loss at somewhere between 0.5-1% of body weight per week. More in my guide on nutrition set up here.

  4. Preston says:

    Hey Andy. I scrolled through the first 40 or so comments and didn’t see anything mentioned about Optimum nutrition EAA’s so forgive me if it has been covered but whey protein always makes me fee sluggish shortly after taking it do you have any thoughts on OP EAA’s? Thanks

    1. Andy Morgan says:

      You can consider EAAs to be the halfway house between whey and BCAAs.

  5. Jeff says:

    Hi Andy

    I typically wake at 8 am, and train roughly around 2 pm. I only drink black coffee during this period. If I take my whey at 1:30 and then start my first meal of the day after training, would this be okay, or am I fasting too long?

    1. Andy Morgan says:

      Totally fine. When having a two meal a day schedule, just try to have at least 6 hours between meals, meaning to have your dinner from ~8 pm onwards.

  6. Tim says:

    A little bit surprised to read such an article here. AFAIK if you consume BCAAs/EAAs/Whey you’re losing your fasted state. What has calories, causes insulin spikes. Why would I do that, if it was my goal to train fasted?

    1. Andy Morgan says:

      If your goal is to train fasted then indeed, you will not consume any calories. However, most people’s goal is not to train fasted, it’s to get jacked and lean. In which case, minimizing the muscle breakdown during workouts when training truly fasted is a more important to the outcome than a temporary spike in insulin.

  7. Adam says:

    Thanks for the article!

    One question: What is your rationale for choosing 25g as the serving of whey protein prior to fasted-training?

    1. Andy Morgan says:

      Prevention of muscle catabolism. More on this in the article.

      1. José says:

        Regardless of (lean) body weight?

        1. Andy Morgan says:

          Muscle protein synthesis maxes out at around ~2.5 g of leucine (which is covered by a 25 g dose of whey), I believe the research has shown this to be independent of total muscle mass (though slightly higher in the elderly, ~3.8 g if I recall correctly, which is ~40 g of whey).

          1. Ira Williams says:

            Great information, but I wanted to piggy back onto this question and ask if you could clarify something.

            I use the Optimum Nutrition Gold Standard Whey which as you said is 24g of protein in the 32g scoop/serving.

            Are you saying I should take 25g of the powder (~19g of protein) or however much gets me to 25g of protein?

            1. Andy Morgan says:

              The latter. Thank you for the question, I could have made that clearer.

  8. Ivan says:

    Hi Andy.
    Thanks for the article, very informative.
    My question is does non-whey protein (pea, soy, hemp protein) also contain the EAA’s plus lactoferrin, beta-lactoglobulin, alpha-lactalbumin, glycomacropeptide, and immunoglobulins

    1. Andy Morgan says:

      EAAs – yes. I haven’t looked into the rest.

  9. Bob says:

    Hi Andy fantastic article. So I love training fasted. The caffeine buzz (coffee/workout) + fasted training = god mode in the gym! Sweet timing being around 2-3 hours after waking up.

    Now…the instant I take in calories I feel a little more “sedated” if you will. Less animalistic.

    This is why I like to just drink coffee or my preworkout (which my contain some bcaa’s) on my way to the gym and I will NOT sip on my whey mix until i start the workout.

    I’m a little concerned about the absorption (I sip on whey during my warmup/activation). Am I being too paranoid here? I know whey starts hitting the muscles/bloodstream after 30 minutes did you say? So if I warmup for 5 minutes then start busting out hard sets, am I not getting the benefits of the whey until halfway into my workout?

    1. Andy Morgan says:

      Ideally, slam it half an hour before your workout. If wake and immediately train, drink it upon waking. Don’t sip it.

  10. Chiranjeev says:

    Hey Andy! I’m currently travelling and don’t have protein supplement atm. I usually train in the morning(5:30,Fasted),drink a cup of coffee before training and Not taking protein shake postworkout either. What could be done in this scenario? I’m currently in cutting phase. Thanks in advance 🙂

    1. Andy Morgan says:

      Just have breakfast after your workout.

      1. CCasey says:

        I’m in similar situation, but i’m very new to IF (as in this is my first day). I have been following Renaissance Periodization for two years before today. I work out at 5am and was thinking i will do the protein before, and then after my work out eat my first meal?

        1. Andy Morgan says:

          Sure, feel free to do that. My full guidelines for meal timing are here.

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