By Dr Joe

I will tackle this question: do BCAAs break intermittent fasting head on, as it seems to bother quite a number people along with lots more questions like : Do BCAAs kick you out ketosis, on this page.

Intermittent fasting is great way to reduce body fat. Intermittent fasting is a fat loss tool and when used correctly can certainly accelerate fat loss.

If you are smart enough to add some serious workout with intermittent fasting, then you can reap some serious muscle gain benefits. And that’s where the BCAAs come into the picture.

Do BCAAs break intermittent fasting?

The answer is, Yes, they do. BCAAs do break a fast during intermittent fasting.
I will explain this in a minute.

do BCAA break intermittent fasting

Branched-chain amino acids (bcaa) are one of the latest raves in the fitness industry. These are supplements designed to supply your body with essential amino acids because your body cannot make them.

BCAAs are designed to assist with your fitness efforts by preserving muscle mass. Most branched-chained amino acids (bcaa) contain the 3 amino acids Leucine, Isoleucine and Valine.

Why is the answer, Yes?

Well, BCAAs are amino acids and amino acids are macronutrients as amino acids make up what we call protein. So, by definition if you take BCAAs supplements either in the tablet form or in the powder form, you are technically “eating”.

By popping BCAA (branched chain amino acids) supplement you are ingesting “food” but a very small amount. Don’t forget that BCAAs have a calorific value.

That said, I do not want you to abandon your BCAA supplements because of what I have just said. You need to look at the bigger picture.

Continue reading to check out the sub-headline ‘The Bigger Picture‘ below on this page, where I put things into context.

For a start, if you are on Ketogenic diet and are worried that BCAAs will kick you out of ketosis, stop worrying. They won’t.
Let me reiterate. BCAAs won’t kick you out of ketosis.Why?

Mainly because BCAAs at the recommended doses of 5 – 10 gm have no significant effect of glucose metabolism. Significant glucose release is necessary for you to be kicked out of ketosis. But that doesn’t happen unless you take a very high dose of BCAA.

But they are not dummy pills or powder either. In truth though, BCAAs have macronutrient value as well as calorific value which would make them technically “food”.

Just to support the viewpoint that you will be breaking your intermittent fasting when you take BCAAs, each gram of BCAA you take has a calorie content of 4 Calories.

1 gm of BCAA = 4 Cal

What this means is; if you take 20 gm of BCAA in the morning, you are indeed consuming 80 Calories without realising you have.

If you take 10 gm of BCAA supplement tablet or powder, you will be consuming 40 Calories.

What this means is BCAA (branched chain amino acid) supplements represent food in their own right. Taking BCCA supplement means you are “eating”. That by extension means taking BCAA during intermittent fasting is ending your fast…technically speaking.

Any Hormone implication?

Well, there is. BCAAs or branched chain amino acids do trigger an insulin response just by virtue of the fact of being small units of proteins themselves.

Don’t forget that one of the objectives of intermittent fasting is to have very low levels of insulin during the fasting interval.

So, if you take a supplement like the BCAAs that has the potential to signal insulin release from the pancreas, you are also technically breaking your fast.

BCAAs by virtue of their potential to trigger insulin release means bcaas break your fast, in the metabolic sense too.

Don’t panic though. The insulin release stimulated by BCAAs is a shallow one. It’s NOT a spike.

Now, let us look at the bigger picture next…

The Bigger Picture
Does the fact that you use BCAAs during your fast really matter in the end?
Probably not, if you do things correctly and get clever too.

You have to remember why is it you are taking the BCAA supplement in the first place.

BCAAs protect you from having muscle loss. They actually help with muscle repair following intense workouts and will help you gain muscle too.

That’s the idea. See my write up on why intermittent fasting BCAAs are necessary here. The advantages far outweigh any downsides.

As I said earlier, there’s no need to worry about the following:

  • Insulin release triggered by BCAA.
  • BCAAs kicking you out ketosis.

Those 2 issues shouldn’t be a problem because they are dose-dependent. The amount of BCAAs you use during intermittent fasting is too small for those 2 events to be of any significance. Fat burning will still happen, if you do things right.

So, here is the work around for your Branched Chained Amino Acids use when fasting. Take your branched chain amino acids or bcaa supplement close to when you are about to break your fast.

That way you will be breaking your fast with the BCAA so close to your meal time that it wouldn’t really matter at all in the grand scheme of things.

Besides, the way I suggest you use your BCAA during intermittent fasting will actually mean the insulin release might be beneficial for your muscle repair and muscle growth, if you adopt my suggested regime.

I prefer a regime of having your workout in the last hour of your intermittent fasting interval. You then follow the workout with your first meal of the day.

Getting clever means you take your branched chain amino acid (BCAA) supplement just before the workout. I talk more about pre-workout bcaa here.

Here is the order:
BCAA supplement ==> Workout (preferably Resistance Training) ==> First Meal of the Day

For clarification, see my suggested use of BCAA during intermittent fasting below.

Below is an example of how you can use bcaa while doing intermittent fasting. This example is based on the 16:8 Intermittent Fasting protocol.

10:45 AM -11 AM 15 minutes pre-workout. Take 10 gm BCAA supplement
11 AM – 12 Noon – Your Training hour
12 Noon – After-workout meal (could represent your largest meal of the day).
3 PM – 2nd meal of the day (Optional. Eating 2 meals is just as fine)
8 PM – Last meal of the day. Fasting begins hereon

With the above example your eating window is between 12 Noon and 8pm. You can have two meals if you like. However, that regime has 3 meals squeezed into the 8-hour eating window.

Nothing to eat from 8pm until 10.45am when technically you are breaking your fast with 10gm of BCAA powder or pills depending on your preference followed by a 1-hour workout session.

Your actual first meal of the day is at Noon which represents a 16 hour fast. The fact that you have the branched-chain amino acid supplement just before your exercise session is a middle ground designed to get you better results for your efforts.

Bcaa does facilitate protein synthesis and boosts metabolism. Nice trade-off.

If you do things this way, you will certainly not derail your fat loss and muscle gain efforts but instead, you will actually be boosting it.

Some BCAA supplement makers have been adding one or two additional ingredients to improve the effectiveness of their products.

For instance, one manufacturer has added Pyridoxine (Vitamin B6) to their formulation to make it more potent. This BCAA is available here on and here

bcaa with vitamin B6


Do you need bcaa for intermittent fasting?

A lot of people also want to know if they should take bcaa during intermittent fasting as a matter of necessity. The answer to that question of the need for bcaas in intermittent fasting is:

It depends on your objectives.

 If you are undertaking intermittent fasting as a way to lose weight overall or simply for weight maintenance, then branched-chain amino acids (bcaa) supplements are not necessary. You can get by with intermittent fasting without having to use bcaa supplements and you can lose weight easily too.

However, if your intermittent fasting objective is to build muscle as well, then bcaa supplements won’t hurt your plan one bit. In fact, they are encouraged.

Yes, you should take bcaa (branched-chain amino acids) supplements during intermittent fasting to maximize not only your muscle gain and but also to prevent muscle loss. My piece on the pros and cons of BCAAs explains more about the benefits of using BCAAs.

Don’t forget that the amino acids in bcaa supplements are essential amino acids which means your body doesn’t synthesize them. You have to get these amino acids through your diet or supplements, especially if your protein intake has gone off whack with the intermittent fasting.

Another important factor is that; intermittent fasting is a calorie-restriction diet as it were. Any form of dieting over time can unfortunately become subtly catabolic. One of the things that happens with the body’s catabolic process is muscle breakdown.

As you restrict yourself to less and less calories, your body will be looking for alternative sources of fuel which usually is fat. Fat burning is the reason you undertook intermittent fasting in the first place.

Problem is after a while, your body will try and recruit protein as source of fuel. Muscle is mainly protein, hence muscle becomes a target for fuel consumption unless you take steps to stop that from happening.

Taking bcaa supplements will help you avoid this unwanted side effect of dieting. Branched-chain amino acids (bcaa) supplements have been shown to help with protein synthesis and prevent protein breakdown.

The involvement of bcaas in protein synthesis and prevention of protein catabolism translates to muscle gain and muscle preservation which is what every bodybuilder wants.

There is also a suggestion that branched-chain amino acids compete with tryptophan to gain access into the brain cells.

This fierce competition with tryptophan which is necessary for the synthesis of serotonin is thought enhance your exercise endurance as the feeling of fatigue is blunted, so you do more for longer.

So it makes sense to use bcaa supplements with intermittent fasting, if your primary goal is muscle building. Having said that, you can get the amino acids in bcaa from a high protein diet. BCAAs are just a short cut to get your essential amino acids.


If you are keen on using BCAAs or are already using these supplements, please do leave me a comment in the commenting section at the very bottom of this article.

I would like you to share your experience with others who visit this page. Nothing beats real-world experience from a variety of people spread across the world over.

If you are new to this, do come back to this page when you start using BCAAs. Bookmark this page and let me know what your experience with BCAAs is.


How does intermittent fasting work?

Intermittent fasting works by tapping into your fat reserves and utilizing them for energy needs. Your body needs energy and it has to be supplied from glucose or glycogen, fat or protein.

The first source of fuel for the body is glucose that is available in circulation. If that glucose is used up, then glycogen which is the stored form of glucose is called upon. When glycogen stored in the liver and muscle cells is exhausted, then the body normally turns to fat.

That is where your fat cells which have been put away for use in times of starvation come in handy. Fat stores are like money put away in a bank vault only to be used up when we have run out of funds for everyday living.

When you run out of money in your current (checking) account, you will turn to your savings account, won’t you?

 The same thing happens with intermittent fasting. During the period of fasting you are going to use up all the available glucose and glycogen, so your body will have no choice than to turn to the next ‘saviour’ – fat. That’s the main mechanism of how intermittent fasting works.

Your body draws on the saved fat stores and starts breaking it up for your metabolic needs. That’s how you lose fat. Naturally the less you eat, the more your body will visit that “fat bank” to grab some more fat to use as a source of fuel.

So, with intermittent fasting you not only lose weight, you lose fat and this has been objectively proven in various research studies, so it isn’t some sort of theory.

Yes, there is science behind intermittent fasting.

Why don’t we start with this science behind intermittent fasting? Krista Varady has been one of the scientists who has done a lot of scientific work in this area.

Krista randomized 32 individuals, (some normal BMI and others overweight) into 2 groups to study the effect of alternate day fasting on body weight, body composition and cardiovascular risk.

Alternate day fasting group were made to eat only between 12 Noon and 2pm on fasting days and only consumed 25% of their normal daily calorie requirements. The next day they ate ad libitum i.e eat as you wish. They fasted on alternate days for 12 weeks.

The control group just ate as usual without any restrictions also for 12 weeks.

 The participants in the  alternate day fasting group dropped their weight by an average of 11 and half lbs over the 12-week period. This average weight loss represented an average of 6.5% of body weight.

Fat loss over the 12-week period was an average of 8 lbs.

Beyond burning your stored fat, intermittent fasting also works by stopping you laying down new fat. This is particularly important as intermittent fasting will help you maintain your weight once you have hit your target weight.

No new fat, no weight gain. Just work on muscle building, if you prefer.

how does intermittent fasting work



How can intermittent fasting prevent cvd, cardiovascular disease?

One thing I like about intermittent fasting is the effect it has on cardiovascular disease (cvd) both directly and indirectly.

The direct effect of intermittent fasting on cvd is on the lipid profile.

 A lot of the studies have pointed to a positive effect on the lipids that are good for us whilst reducing the lipids that are bad for us.

For instance, that Varady study I talked about about did show that after 12 weeks of alternate day fasting, the LDL cholesterol (bad cholesterol) and the triglycerides levels were much lower in the participants that fasted compared to the control groups that did not fast.

The only disappointment in that study was the HDL cholesterol (the good cholesterol) did not change.

Another study that randomized 54 individuals to intermittent fasting calorie restriction liquid-based and the other group food-based over a 10-week period using the same intermittent fasting protocol. The only difference was giving one group liquid and the other solid food.

There was consistent reduction of total cholesterol as well as LDL cholesterol (the bad cholesterol) in both the liquid food group and the solid food group. The only difference was that the liquid food group had a slightly better profile compared to the solid group.

Inflammatory agents like interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and insulin-like growth factor-1 (IGF-1) decreased in theliquid based group. These inflammatory factors predispose an individual to heart attacks.

This review showed that Total cholesterol and the fat that causes a lot of damage (Triglycerides) were lowered by the act of fasting in men. It also supported the finding from the other study that High density lipoprotein (HDL cholesterol) gets elevated during fasting especially in women.

You can see from those studies that the claims being made in the sphere of intermittent fasting are backed by science, not just theory.

Indirectly, intermittent fasting does increase the sensitivity of tissues to glucose uptake from the circulation. This has been shown in many studies.

Individuals who undertake intermittent fasting can improve their insulin sensitivity by a mile.

> Intermittent fasting also promotes a reduction in fasting insulin levels. The combination of lower blood glucose levels, lower insulin levels means obesity is kept at bay. Remember low insulin levels means fat storage is discouraged as insulin is a fat preserver.

Preventing obesity means eliminating one risk factor for cvd, cardiovascular disease.

If you put everything intermittent fasting does together i.e prevention of obesity, reversing insulin resistance, lowering total cholesterol levels and bad cholesterol levels (LDL), raising HDL (good cholesterol), lowering triglycerides levels, lowering inflammatory agents etc, all of which are risk factors for cvd, cardiovascular diseases, heart attack and stroke, you can now begin to see how intermittent fasting prevents or even reverses these killers.

What’s your experience with BCAAs like? I would like to know. Don’t forget to leave me a comment below. Thanks

Suggested further reading:
How to Avoid Complicated Diet Rules and Prevent REBOUND Weight Gain