Pre-workout supplements are one of the most popular supplement categories out there. They’re hip, they’re cool, they come in delicious flavors and they power you through your workouts.

Intermittent fasting, or periods of not eating, is also becoming more and more popular, with emerging science on IF related to everything from fat loss, to longevity, to cancer prevention.

If you combine the two together, then it leaves us with the question: will a pre-workout break your fast?

Obviously, eating a big meal will break your fast, but what about drinking your favorite pre-workout supplement? The answer, as usual, is sort of and it depends.

What Is Fasting and Why Is It Necessary (and helpful)?

Fasting has different definitions. For example, religious fasting often means not even drinking water. For rules on religious fasting, consult your religious authority, not some stranger on the internet.

Our interest lies in fasting on a physiological level. For us, a better way to define fasting is to look at your blood sugar and insulin levels.

When we eat, our body produces insulin, and our blood sugar rises. This also happens when we drink beverages like soda, which have lots of sugar, and therefore produces an aggressive insulin response.

Many of the benefits of fasting revolve around reducing this insulin response.

Depending on what’s in the pre-workout, then, you may get a negligible, or not so negligible, insulin response. That’s because they may contain ingredients that are insulinogenic.

So Will Any Insulin “Break Your Fast?”

This is where it gets tricky. Breaking a fast is not a switch. It’s not like you’re either fasting or you’re not, and any amount of insulin will get you out of this fasting state. There’s nuance to this. Sure, artificial sweeteners may boost insulin, but the increase may be small enough that it doesn’t matter, especially depending on your goals.

Keep this in mind throughout. For many of the pre-workout supplement ingredients we’ll touch on, they’re in the “gray area,” and you’ll have to decide based on your goals.

What Ingredients in Pre-Workouts Are Insulinogenic, and Therefore May Break Your Fast

Here are the insulinogenic ingredients that may be in your pre-workout.


Most pre-workout supplements these days are don’t have more than a gram or two of sugar. However, if your pre-workout does, like many energy drinks, then it’s going to break your fast.

If you’re trying to train fasted, stay away from sugar.

Amino Acids

Amino acids are one of the gray area ingredients. To some extent, amino acids do create an insulin response, but it depends on the amino acid. For example, the branched-chain amino acids (BCAAs), leucine, isoleucine, and valine, have been shown to have the highest insulin response.

On the other hand, though, when you’re fasted is when you may really benefit from the anabolic benefits of BCAAs, which may help reduce muscle protein breakdown.

Aside from the BCAAs, the rest of the essential amino acids, those which your body can’t produce on its own, have the highest insulin responses.

Other amino acids leave a much more negligible, if existent at all, effect. Fortunately, this includes pre-workout staples like beta-alanine, creatine, and citrulline.

Sugar-Free Sweeteners.

This is another big gray area. Even sugar-free sweeteners, whether it’s artificial like sucralose, or natural like stevia, cause an insulinogenic reaction in our body.

This is partly because when our tongue tastes something sweet, it causes an insulin reaction. Even though there’s no actual sugar, we’ll still get a bit of an insulin response.

Again, it’s a gray area, so it depends on your goals and how much you want to limit or eliminate insulin.

What Ingredients in Pre-Workout Supplements Won’t Break Your Fast

Luckily, there are lots of ingredients that won’t cause any, or a totally negligible, insulin response.


Caffeine is a staple in pre-workouts. This fact alone makes simple black coffee a good pre-workout option. If you can’t drink blank coffee, then buy higher quality coffee that actually tastes good, and quit being a little child who needs everything to be sweet.

If you want an extra buzz without any insulin response, you can add kratom to your coffee.

In fact, caffeine is a great idea if you’re going to work out fasted, because it’ll give you an energy and performance boost that you’ll be more likely to need, since you haven’t eaten.

You can also take a caffeine pill pre-workout, instead of a traditional pre-workout supplement.


Beta-alanine is a staple in pre-workouts for its muscular performance benefits. Luckily, it won’t affect your insulin levels.

It’s also the ingredient that causes the “itch” in pre-workouts.


Creatine also won’t affect your insulin levels. It’s one of the most proven supplements out there for performance. It also has interesting research on depression.


Finally, citrulline, which will help improve your muscle pumps, doesn’t disprove of your intermittent fasting diet.

Between these ingredients, you can create your own little pre-workout stack, since beta-alanine, creatine, and citrulline are all available in unflavored powders and pills.

That’s one solution to the conundrum that strikes a balance.

All in All, Will Pre-Workout Break My Fast?

The answer is sort of and it depends on the pre-workout.

One without BCAAs and artificial sweeteners probably won’t, but this is not so easy to find. A better solution is to buy simple ingredients and create your own pre-workout.

Should You Worry About Being Fasted In the First Place?

Training fasted is a hotly controversial topic. There are huge proponents of it, and those who say it’s better to get some fuel in you before working out.

We’re not going to come down hard on it, but generally speaking, if you have more strict fat loss goals, then you’ll want to avoid the insulin spikes, even the little ones caused by things like BCAAs and artificial sweeteners.

However, if you’re trying to build muscle, and aren’t as concerned with fat loss, then the benefits of something like BCAAs, which can turn on muscle protein synthesis, may outweigh the costs.

Like anything, you have to make the decision for yourself.