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Do BCAAs Break a Fast? The Truth About Amino Acids

Tyler Sellers
Published by Tyler Sellers | Senior Coach
Last updated: August 14, 2023
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Branched-chain amino acids (BCAAs) are essential amino acids. Because it’s a necessary part of your diet, I understand the confusion on if it breaks your intermittent fasting.

I also get asked if consuming BCAAs during a fasted state has any benefits.

You don’t want to mess up something like fasting and end up hurting your body. I did some research to find out how BCAAs can affect your body if you're fasting.

Quick Summary

  • BCAAs can break a fast because they are amino acids, which build proteins, and that is how they break your fast.
  • Scientifically, BCAAs have been proven to reduce physical and mental fatigue after intermittent fasting.
  • Intermittent fasting is voluntarily abstaining from food for a specific period.
  • Taking BCAAs for long while breaking intermittent fasting can significantly help lower blood sugar levels.

Do BCAAs Break A Fast?

holding BCAA Scoop

Yes, BCAAs do break a fast.

For now, let’s discuss why branched-chain amino acids break a fast. There are a couple of factors.

The first is that you should consider it’s calorie content.

Note that a full dose BCAA supplement contains about 4g of BCAA, so considering the math, a serving would amount to 20 calories in total.

That’s almost an insignificant amount of calories compared to a pre-workout supplement.

The second factor is that BCAA is an amino acid. It’s a macronutrient. It doesn’t matter if it’s in a pill or powder form because the amino acids will still help you build protein, which is why it breaks your fast.

One gram of BCAAs usually has almost five calories. If you’re consuming calories, then you are technically eating.

However, I think the benefits of taking BCAA during a fasted state is more beneficial than not taking it. I’ll discuss that in a minute.


What Does It Mean To Break A Fast?

Fasting means to abstain from food for a specified period. Some people do this for religious reasons, while others are interested in the potential health benefits.

If you are breaking a fast, it means that you are ending the period of abstaining from food. If you eat, then you’re not fasting.

There are a few exceptions that don’t end the fast. For example, water or tea is ordinarily okay to drink while on a fast.

What Are The Benefits of BCAAs?

plate weighing scale

BCAAs are a popular supplement for muscle building. It gives you the energy to take your training session to the next level.

Proper protein intake in your diet should get you enough BCAA intake, but sometimes a supplement is needed. You will find that combining whey protein and BCAA gives you the greatest boost.

BCAA supplements have an amino acid called leucine, which is essential for muscle protein synthesis. Protein synthesis helps your body produce new cells and prevent a protein breakdown. You don’t want a muscle breakdown if you’re looking to build muscles.

Here are the most common benefits of these amino acids:

  • Increase Muscle Mass: Most people take BCAA for muscle building. Research supports that BCAA is excellent for increasing muscle tissue [1].
  • Decreases Muscle Soreness: Anyone can tell you that going hard with resistance training means sore muscles. BCAA can help reduce soreness and may help with muscle damage.
  • Reduce Physical And Mental Fatigue: Not only can it help with physical fatigue, but BCAA supplements can also help keep your mind alert. It allows you to work out longer, which means that you can improve your muscle growth.
  • May Lower Blood Sugar Levels: It can affect your insulin levels. There have been studies that suggest there is an insulin response to BCAA by causing your muscles to absorb more sugar and decreasing your blood glucose levels.

What Are The Benefits of Fasting?

alarm clock and plate

There are a few benefits behind intermittent fasting. I was happy to find some research to back-up those claims too.

1. Reduce Insulin Resistance

Your body also produces an insulin response while in a fasted state. Fasting leads to a drop in insulin levels, which can lead to an increase in fat burning.

It can also reduce the resistance of insulin that can promote insulin sensitivity. It allows your body to regulate your blood sugar levels by transporting glucose to your cells.

2. Lose Weight and Fat Loss

Fasting can help you lose weight. It’s not surprising that you end up with fat loss since you are abstaining from calories.

Fasting can lead to lower rates of muscle glycogen levels. Muscle glycogen is used for energy. Your body starts to break it down for glucose to deal with the lower rates of insulin. It triggers the loss of water weight.

Fasting can also boost your metabolism, which could speed up the process of losing body fat [2]. It does all of this without muscle loss.

3. Fights Inflammation

It’s possible that intermittent fasting can lead to decreased levels of inflammation. It’s good to prevent inflammation since it could reduce the chances of developing chronic conditions like heart disease or arthritis.

heart and lifeline

4. Could Improve Heart Health

Some research suggests that fasting can help with promoting good heart health.

One study showed that fasting led to lower blood pressure and decreased levels of cholesterol [3].

5. Boost Brain Function

There are a few studies that show there are potential health benefits for your brain and central nervous system.

Most studies have only been done on animals, so there needs to be more research conducted on the benefits for humans. So far, fasting could potentially help with the growth of nerve cells that could lead to better brain function [4].

6. Live Longer

Fasting isn’t precisely the fountain of youth, but animal studies suggest that you could live longer and slow down the process of aging [5]. It’s a promising benefit, but I wouldn’t say fasting alone could help your longevity.

How Does Fasting Work?

fruit juice

The most common fasting method is to abstain from food and only drink water. There are a few other variations.

You could choose only to have vegetable or fruit juice.

There is also “partial fasting”, which involves removing certain foods from your diets like processed foods or caffeine.

There’s more than one way to do intermittent fasting. One is not necessarily more effective than the other. It’s more of a matter of determining which is a better choice for you.

Here are six popular methods.

  1. The 16/8 Method: This method is probably the most popular. You fast for 16 hours a day and then eat during an 8-hour window during the day. If you have a late dinner and skip breakfast, then this is a doable option. It’s not recommended for women to fast for 16 hours. Instead, it’s preferable to fast for 14-15 hours and have a 9-10 hour eating window.
  2. Eat-Stop-Eat: Do a 24-hour fast once or twice a week. The most important aspect of this method is not to eat more than you usually do when you end your fast. It takes some discipline to fast for 24 hours, so it may take some time to build up your efforts for this.
  3. The Warrier Diet: Instead of abstaining from food completely, you limit yourself to eating small amounts of fruits and vegetables. Then you have a 4-hour eating window (usually around dinnertime) to have a large meal.
  4. The 5:2 Diet: In this method, you eat five days a week. Then on the other two days of the week, you restrict your calories—500 calories for men and 600 calories for women. There’s not a lot of research to support this method.
  5. Alternate-day: Every other day, you fast for 24 hours or eat only a few hundred calories. It doesn’t seem sustainable, especially in the long-term.
  6. Spontaneous Meal Skipping: Instead of a structured fast, you could opt to skip meals occasionally. For example, if you’re too busy to eat or when you aren’t hungry. It’s essential to make sure you get your daily nutrition from the other two meals in your day if you follow this idea.

The key with fasting is to stick to a regular structure. I have seen individuals erratically fast based on their schedule and then get frustrated when they don’t feel or see the benefits. If fasting is a tool someone is going to utilize, life has to fall in line with it, and if it doesn’t, that might be a sign you need to rethink it.
- Sydney Greene, MS, RD

What Happens When I Take BCAAs While Fasting?

man fasting

Remember that taking BCAAs means you are going to end your fast. Many people choose to consume amino acids anyway to prevent muscle loss.

If you’re going to exercise while fasting, then taking some of our recommended BCAAs may help you with energy.

I mentioned before that fasting leads to lower levels of glycogen and, therefore, lower levels of energy. BCAAs can boost your energy levels and help you get through a workout.

You should always proceed with caution if you are going to exercise without consuming food. It’s best to discuss this with a health professional.


man holding tumbler

Do BCAAs Trigger An Insulin Spike?

BCAAs can trigger more insulin but it’s not considered a spike. I know people worry about this if they are looking to lose weight. It promotes fat loss by reducing insulin levels and taking BCAA can increase your insulin.

So do they cancel each other out?

Nope. BCAA doesn’t increase your insulin enough to remove your body from a fat-burning state.

Can You Build Muscle While Fasting?

You can build muscle while fasting, but it’s incredibly difficult. Bodybuilding intermittent fasting protocol doesn’t exist. It leads to reduced calories, and it may be harder to get enough protein.

Fasting is a better option for those looking to lose or maintain their body weight.

Will I Lose Muscle If I Fast?

You won’t have muscle loss if you fast. One study found that fasting was able to decrease body fat without losing muscle [6].

As long as you do weight training, then you won’t lose your muscle. You could lose your body composition if you didn’t exercise to keep muscles in shape.


Amino acids are essential to support your muscles. Branched-chain amino acids are well-researched to help with muscle growth and reduce soreness.

Here are recommended list of BCAAs for men and women:

Even though BCAAs means that you are technically breaking a fast, it does offer benefits that you can’t ignore. The ability to reduce the loss of lean muscle and to boost your energy for workouts can make a huge difference.

I think if you are looking to build muscle, there are better diets than fasting. It’s possible, but it seems like it would take extra work than necessary.

If you are looking to lose weight, then fasting is a good diet option to consider. You could also support your body by taking an amino acid like BCAA.

What are your thoughts about taking BCAA while abstaining from food?


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