Will Pre-Workout Break My Fast? Maybe, Here's How

published by: Debbie Luna
Last Updated:
October 6, 2022

With the recent growth in popularity that fasting diets have seen, its no surprise that quite a few fitness enthusiasts have started to question whether their favorite pre-workout supplement is breaking the rules of their diet.

Unfortunately, much like any other question in bodybuilding and nutrition, the answer is that it depends.

Your pre-workout will likely break your fast if it contains any sort of caloric value, especially simple carbohydrates that will be rapidly metabolized by the body. Otherwise, if your pre-workout has no compounds in it that can be considered “food” so to speak; it will not break your fast.

What are Pre-Workout Supplements?

The term pre-workout supplement refers to a specific type of food product meant to prime the body of an individual prior to intense exercise.

gorilla mode energy preworkout
Deb's Gorilla Mode Energy by Gorilla Mind

These products usually contain a variety of different compounds meant to increase central nervous system arousal and cardiovascular function, such as caffeine, various B vitamins and beta alanine.

Pre-workouts vary between brands and individual serving sizes, but will generally include one to two stimulant compounds, food coloring, and some sort of flavorant that masks the otherwise unpleasant taste of the rest of the ingredients.

Why Do People Use Pre-Workout?

The majority of exercisers use pre-workout supplements to improve their general performance, as a number of compounds normally found in pre-workout supplements like caffeine, BCAAs and creatine are all clinically established to improve physical performance in short order.

Pre-workout supplements are designed to sustain an exerciser throughout their workout, improve their post-workout recovery and enable them to function at a higher physical level temporarily.

What Constitutes a “Fast”?

Fasting is a metabolic state wherein an individual has gone for a prolonged length of time without any sort of caloric intake, causing biochemical changes within their body that can provide several health benefits.

In modern times, the most common form of fasting is in a diet called intermittent fasting (IF), where individuals will not eat for a specified portion of a day so as to reduce their total caloric intake alongside other metabolic benefits.

Fasting is generally performed by modern gym goers as a method of reducing their total body fat, or otherwise increasing their quality of life through the aforementioned metabolic benefits. 

This is the reason why pre-workout possibly affecting the fastest state is of such importance to so many people, as they worry that their favorite workout enhancing supplement is ruining said benefits.

The Science of Breaking a Fasted State

In most cases, when one refers to a fasted state, they mean an extended period of time without the individual consuming anything of caloric value.

While clinical studies are unsure of exactly how many calories are sufficient to break a fasted state, we can generally assume that anything more than 30-50 calories is enough to do so.

Though the majority of pre-workouts don’t contain this many calories in a single serving, it is entirely likely that they can come close to this amount, potentially breaking your fast depending on the sort of ingredients and additives mixed into your pre-workout.

Ideally, if you want to make absolutely sure that a pre-workout will not break your fast; purchase one with little to no caloric value per serving. This will ensure that it is impossible your fast is broken by your pre-workout supplement.

How to Tell if Your Pre-Workout Will Break Your Fast

The best way to ascertain whether your pre-workout supplement will break your fast is to look at the nutrition facts on the label.

gorilla mode energy supplement facts
Supplement Facts from Gorilla Mode Energy

Going by the serving size (usually 1-2 scoops), if the calories are marked as anything in the double digits, it is possible that your pre-workout can ruin the fastest state that you are in.

Due to the laws of certain government bodies, supplement companies are also given some leeway as to how many calories they can round down per serving, with certain brands of pre-workout supplements marking the caloric value of their product to be 0 when it can in fact be 5 calories. 

If using multiple servings of such pre-workout brands, it is best to err on the side of caution and account for this discrepancy.

For instance, the above pre-workout doesn't mention anything in regards to calories per serving. However, upon messaging them, their support agent notes:

calories in gorilla mode energy

Meaning, 1 scoop of Gorilla Mind (4.9g) has roughly 20 calories.

If your pre-workout doesn't stipulate the number of calories on the container or on the supplement facts, be sure to reach out to the Company directly.

A Side Note to People Fasting for Weight Loss Alone

For individuals fasting simply to aid in weight loss, there is no need to worry about your pre-workout breaking your fast. 

This is simply because of the fact that the fastest state does not have a significant enough impact on your rate of caloric expenditure to actually influence fat loss - meaning that, unless you are taking advantage of the other benefits of fasting, it shouldn’t matter whether your supplements break your fastest state or not.

In fact, it is possible to argue that the elevated heart rate and improved performance brought on by pre-workout supplements is more than advantageous for achieving your particular goals.

Frequently Asked Questions (FAQ)

Will Pre-Workout Kick Me Out of Ketosis?

Much like a fasted state, whether or not a pre-workout supplement can ruin your state of ketosis will depend on what ingredients are used to make the pre-workout.

Though a fastest state is governed by how many calories you eat, ketosis is also affected by the carbohydrate intake of your diet as well. 

Generally, any more than 50 grams of carbohydrates within a day is enough to kick you out of ketosis. Fortunately, most pre-workouts do not come anywhere near this amount, and as such will likely not ruin your keto diet.

Will 10 Calories Break a Fast?

While it is unlikely, some publications do indeed claim that 10 calories alone are sufficient enough to ruin a fasted state. 

If you would like to err on the side of caution and make absolutely sure that you remain properly fasted, it is best to avoid any sort of calories in their entirety.

What is Dirty Fasting?

Dirty fasting is the more common form of fasting, wherein a certain (albeit small) number of calories are still consumed by the participant. 

This is opposed to strict or clean fasting, where absolutely no calories are allowed to be consumed, ensuring that the participant remains in a completely fasted state.

In Conclusion

And there you have it - a definitive way to tell if your particular pre-workout brand will break your fast. 

Taking a quick glance at the nutrition facts on the label should be more than enough to clue you in. 

If there are indeed calories and if you want to remain in a strictly fasted state, then it's probably best to stick with just water or black coffee.

Otherwise, one or two scoops shouldn’t hurt your results too much. 


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2. Kaczka P, Batra A, Kubicka K, Maciejczyk M, Rzeszutko-Bełzowska A, Pezdan-Śliż I, Michałowska-Sawczyn M, Przydział M, Płonka A, Cięszczyk P, Humińska-Lisowska K, Zając T. Effects of Pre-Workout Multi-Ingredient Supplement on Anaerobic Performance: Randomized Double-Blind Crossover Study. Int J Environ Res Public Health. 2020 Nov 9;17(21):8262. doi: 10.3390/ijerph17218262. PMID: 33182295; PMCID: PMC7664913.

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Debbie (Deb) started powerlifting and Olympic lifting in High School as part of her track team's programming; She continues to train in order to remain athletic. Inspire US allows Deb to share information related to training, lifting, biomechanics, and more.
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