Does Pre Workout Break a Fast?

Pre-workout supplements have become one of the top-selling workout supplements in the world over the past few years.

Their rise has also coincided with several other fitness trends, with intermittent fasting being a prime example. 

In case you aren’t familiar with it, intermittent fasting is a diet protocol that involves alternating between periods of fasting (refraining from caloric food and drink) and eating.

Of course, this means many popular drinks—soda, energy drinks, sugar-filled coffees, etc. are off limits during the fasting period. Does this mean pre-workout drinks are verboten, too, though? Does pre-workout break a fast

There’s no simple yes or no answer to this question, as it depends on what kind of fast you’re practicing (for religious or health reasons) and what kind of pre-workout you’re consuming. 

Read on to find out which pre-workout supplements do and don’t break your fast.

What Is Pre-Workout?

A pre-workout is a supplement that’s meant to be taken about 30-to-60 minutes before training to boost your performance. Typically, pre-workout supplements contain a mix of ingredients, like caffeine, citrulline malate, and beta-alanine that increase strength, endurance, and focus and reduce fatigue.

That said, you can find all manner of other ingredients in pre-workout supplements, from nootropics and obscure plant extracts, to branched-chain amino acids (BCAAs), to artificial food dyes and sweeteners. 

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What Is Fasting?

In a general sense, a “fast” is a period of time during which you abstain from eating (and drinking, in some cases), often for religious reasons.

When people refer to fasting in a fitness sense, however, they’re generally referring to intermittent fasting, which involves cycling between periods of fasting and eating, normally on a regular schedule.

For instance, one popular intermittent fasting diet has you fast for 16 hours per day and eat during the remaining 8 hours.

Another calls for 20 hours of fasting with a 4-hour feeding window, and yet another entails fasting for 24 hours once or twice a week, then eating normally on the 5 or 6 days.

“Fasting” in this sense, doesn’t just refer to periods of time that you refrain from eating—it has to do with how your body processes and absorbs the food you eat.

When you eat food, it gets broken down into various molecules that are released into your blood. From there, the hormone insulin shuttles these molecules into cells.

When your body is digesting and absorbing what you’ve eaten, and insulin levels are still high, your body is in a fed or postprandial state (prandial means having to do with a meal). 

Once your body is finished processing and absorbing the nutrients, insulin levels drop to a minimum (baseline) level, and your body enters a fasted or postabsorptive state. 

How long it takes for your body to reach this fasted state depends on the size and composition of your meal, but as a rule of thumb, you won’t be truly “fasting” until you haven’t consumed anything containing calories for at least six hours.

Does Pre-Workout Break a Fast?

It depends. 

I know, probably not the answer you were looking for. 

Let’s break it down, though:

First, it depends on why you’re fasting.

If you fast for religious reasons, and must abstain from all forms of food and drink, then drinking a pre-workout will break your fast. 

If you’re following a fasting protocol such as intermittent fasting, alternate-day fasting, or the 5:2 diet for health, fitness, or weight loss purposes, then whether or not your pre-workout breaks your fast depends on the ingredients it contains.

Generally speaking, the performance-enhancing ingredients in pre-workout supplements don’t contain calories and thus won’t break your fast. 

(An exception to this rule is branched-chain amino acids which do contain calories, and will raise insulin levels enough to break a fast.)

The problem is, they don’t always taste particularly good—you’ll know this all too well if you’ve ever chugged a serving of unflavored beta-alanine before a fasted workout.

To combat this, supplement companies include various sweeteners and flavors such as sugar (and sugar alcohols such as sorbitol, maltitol, and xylitol), dextrose, and maltodextrin to make their products more palatable.

However, many of these ingredients contain calories that raise insulin levels, and thus break your fast when you consume them. For example, sugar, maltodextrin, and amino acids all raise insulin levels, and will break your fast. 

Thus, if you want to ensure your pre-workout won’t break your fast, a good rule of thumb is to make sure it has few or no calories. For instance, if your pre-workout supplement has 5 calories per serving (like Pulse), that’s probably fine, as it will have almost no impact on insulin levels. If it has 20, 40, or more calories, though, then it will raise your insulin levels even higher and will cancel out some of the effects of fasting. 

(It’s worth noting that when it comes to fat loss, the only real benefit of intermittent fasting is that it makes it easier for some people to control their calorie intake. Thus, “breaking” your fast with a few calories from a pre-workout isn’t going to banjax your weight loss efforts so long as you remain in a calorie deficit). 

Pre-Workout Ingredients that Won’t Break Your Fast

As you now know, the main pre-workout ingredients that will break your fast are the ones that contain calories, typically amino acids or sugars. That said, most pre-workout ingredients don’t contain calories and thus won’t break your fast. Let’s go over the main ones.

(And if you’d like even more specific advice about which supplements are right for you, take the Legion Supplement Finder Quiz now.)


Research shows that caffeine boosts metabolism, improves strength, promotes muscle endurance, and enhances anaerobic performance. 

If you want a clean, delicious source of caffeine that also contains five other ingredients that will boost your workout performance, try Pulse (you can also get caffeine-free Pulse, too).


Creatine is a compound made up of the amino acids L-arginine, glycine, and methionine

Research shows supplementation with creatine . . .

  • Boosts muscle and strength gain
  • Improves anaerobic endurance
  • Reduces muscle damage and soreness from exercise
  • Increases the amount of glycogen your muscles can store
  • Helps preserve lean mass and strength while restricting calories

If you want a 100% natural source of creatine that also includes two other ingredients that will help boost muscle growth and recovery, try Recharge.

Citrulline Malate

Citrulline malate is the amino acid L-citrulline bound with malic acid, which turns into another amino acid in the body known as L-arginine.

Research shows that supplementation with L-citrulline malate improves muscle endurance, relieves muscle soreness, and improves aerobic performance.

If you want an all-natural citrulline malate supplement that also contains five other ingredients designed to increase energy, improve mood, sharpen mental focus, increase strength and endurance, and reduce fatigue, try Pulse.


Beta-alanine is a naturally occurring amino acid that reduces exercise-induced fatigue and increases the amount of work you can do in your workouts.

If you want a 100% natural beta-alanine supplement that also contains five other ingredients designed to get you fired up, zeroed in, and ready to crush your workouts, try Pulse.


L-theanine is an amino acid found primarily in tea that’s responsible for some of its health benefits.

Research shows that supplementation with L-theanine reduces the effects of mental stress, increases the production of nitric oxide, and improves mood, memory performance, and attention when paired with caffeine.

If you want a 100% natural L-theanine supplement that can boost your physical and cognitive performance with no side effects, try Pulse.

Alpha-glycerophosphocholine (Alpha-GPC)

Alpha-glycerophosphocholine (also known as alpha-GPC and glycerophosphocholine) is a compound that contains two molecules known as choline and glycerophosphate.

While Alpha-GPC mitigates cognitive decline as we age, on the performance side of things, research shows it increases power output and increases growth hormone levels.

If you want an all-natural source of alpha-GPC, that also contains clinically-effective doses of five other ingredients designed to help you perform at your best, try Pulse.


Betaine (also known as trimethylglycine) is an amino acid found in various foods like beets (hence the name), spinach, and quinoa.

Although betaine’s physiological functions aren’t fancy, they’re beneficial during times of physical stress, and this is why research shows that supplementation with it boosts muscle endurance and increases strength.

If you want a 100% natural source of betaine that also contains five other ingredients that enhance your athletic performance, try Pulse.

If you’d like to learn more about which Legion supplements are right for you, check out the Legion Supplement Finder Quiz here.

+ Scientific References

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