Isaac Robertson
Published by Isaac Robertson
Fact checked by Donald Christman, BHSc FACT CHECKED
Last updated: May 18, 2021

Many of my clients have complemented their exercise routine with a pre-workout supplement and one of the intermittent fasting protocols to help them achieve their weight loss and fitness goals faster.

However, they’ve read many online debates presenting conflicting views about whether a pre-workout breaks your fast or not.

(Honestly, finding the best pre-workout supplement while intermittent fasting is tricky.)

And now they’re worried that drinking pre-workout supplements will disrupt their fasting metabolism and interfere with their fasting results.

Is there a reason to be worried?

We’ve done thorough research to answer this and other hot questions on the topic and provide the best advice.

Here’s all the key information you should know.

Does Taking Pre-Workout Break Your Fast?

Spilled supplements on a container

The answer to the question: “Does a pre-workout break your fast?” isn’t that straightforward.

Some pre-workouts can break your fast, even if they’re low-calorie products. It depends on a particular pre-workout blend and brand.

The best way to figure it out is to learn which ingredients in a pre-workout break your fast.

So, let’s dive into the most common pre-workout information, health and fitness benefits, and the way they affect intermittent fasting.

3 Ingredients That Disrupt Fasting

Pre workouts stored in a plastic

1. Sugar, Artificial Sweeteners, and Other Carbohydrates

Most pre-workout supplements naturally taste awful.

So, manufacturers often add sugar, dextrose, sucralose, or various other natural or artificial sweeteners with flavors like blue raspberry, green apple, citrus, candy, etc., to mask that bad taste, enhance the product texture and color.

Besides enhancing flavor, sugar is also used in pre-workouts to provide additional energy.

Regular table sugar triggers an immediate insulin response, kickstarting your metabolism and throwing you out of the fasted state.

Although some recent research suggests that low-energy artificial sweeteners don’t have the same effects on your blood insulin levels [1], the data from numerous studies have shown that any zero-calorie sweetener can also cause an insulin spike, activating your digestion and breaking your fast.

Although this issue is hotly debated in scientific circles, many artificial sweeteners, flavors, food dyes, and similar content variations used in pre-workout supplements are carcinogenic, can disturb your gut microbiome, and cause various health problems, which works neither in favor of intermittent fasting nor your overall health benefits. [2] [3] [4]

So, it’s wise to avoid any sugars, carbs, artificial or “natural” sweeteners, thickening agents, preservatives, and additives to make the most out of your intermittent fasting regimen.

2. Whey Protein

Pre-workouts that contain whey protein will also mess up with your fasting because whey protein contains calories.

As you probably know, it isn’t allowed to consume anything with more than 40 or 50 calories while intermittent fasting if you don’t want to break it.

3. Amino Acids

Supplements on a person's hand

Almost all pre-workout supplement blends on the market contain one or another amino acid type.

They contain a certain amount of calories.

Moreover, proteinogenic amino acids are proven to spike your insulin level, activating protein synthesis pathways in your brain and signaling that you’ve consumed food. [5]

Proteinogenic amino acids include the following essential and non-essential ones:

  • BCAA (Leucine, Isoleucine, and Valine)
  • Lysine
  • Threonine
  • Phenylalanine
  • Histidine
  • Methionine
  • Tryptophan
  • Arginine
  • Tyrosine
  • Alanine
  • Cysteine
  • Glycine
  • Asparagine
  • Serine
  • Proline
  • Glutamine
  • Glutamic acid
  • Aspartic acid

So, consuming these substances would technically kick you out of a fasted state, ruining your intermittent fasting gains such as gut rest, metabolism boost, autophagy, etc.

However, it’s not all black and white.

Even though you should avoid the above amino acids while intermittent fasting, you can still benefit from non-proteinogenic supplements like:

  • Beta-Alanine
  • Creatine
  • Betaine
  • Carnitine
  • D-aspartic acid

They won’t break your fasting as they don’t contain any calories, macronutrients, artificial sweeteners, flavors, etc., that cause an insulin response.

Even better:

They may help you feel less tired during intense workouts and enhance your exercise performance and capacity.

4 Ingredients That Won't Break a Fast

Caffeine and different supplements on ground

1. Caffeine

Caffeine is among the most common compounds found in many pre-workout supplements.

Good news:

You can enjoy your morning coffee (black, unsweetened, without milk or creamer), green tea (if you like its taste more), or even caffeinated pills in moderate amounts (100-300 mg/day) without breaking your fast.

Even better -  You can reap a lot of other benefits of caffeine [6] [7], such as:

  • Increased energy levels
  • Enhanced oxidative stress induced by training
  • Enhanced physical performance
  • Improved endurance
  • Better focus and alertness
  • Curbed appetite
  • Faster calorie and fat burn
  • Antioxidant effects
  • Increased effectiveness of autophagy (due to faster removal of glycogen stores from your blood and metabolizing fatty acids faster)

2. Creatine

This is another ingredient the majority of available pre-workout supplements contain.

It’s calorie-free and doesn’t raise your insulin levels, so you can safely use it as it won’t break your fast.

In addition, it can help boost your energy levels, providing more strength to ensure muscle gain and better exercise capacity in the next high-intensity gym session. [8]

3. Beta-Alanine

Beta-Alanine aids in building muscle mass by boosting your level of carnosine. The tingling effect you may feel after drinking a pre-workout supplement comes from this substance.

“Beta-alanine is commonly used by mouth for improving athletic performance and building lean muscle mass in younger adults, and improving physical performance in elderly adults.” -WebMD

Consuming it also doesn’t mess up with any intermittent fasting protocols.

4. Citrulline Malate

Plenty of pre-workouts contain Citrulline Malate, as well. It also doesn’t interfere with your fasting.

It works as a vasodilator, meaning that it improves your blood flow by increasing nitric oxide level. Consequently, your muscles get a better nutrient supply for better pump results.

FAQs

How Many Calories Will Break a Fast?

According to a general thumb rule, more than 50 calories will break a fast. Any intake below that will safely keep your body in a fasted state.

Will Lemon Water Break Your Fast?

No, lemon water won’t break your fast because it’s calorie-free, and it doesn’t increase your insulin levels.

What’s more, lemon water with sodium from Himalayan pink salt aids in detoxification and balancing the electrolytes in the body.

But, we’re not talking about sweetened lemonade or caloric water with lemon or other flavors you can find in a supermarket, among other sports drinks.

Does Coffee Break a Fast?

No, black coffee doesn’t break your fast if you drink it unsweetened, in moderate amounts - one or two cups (240-470 ml) without any other added ingredients. [9]

Does Green Tea Break a Fast?

No, green tea doesn’t break your fast unless you add honey, sugar, creamer, or milk to it.

Does Creatine Break a Fast?

No, creatine doesn’t break your fast as it contains no calories.

Can I Take a Fat Burner While Fasting?

Yes, you can take most fat burners while intermittent fasting as they shouldn’t contain anything that can break your fast.

Bottom Line on Pre-Workouts and Intermittent Fasting

In conclusion, the best way to ensure you’re taking a pre-workout product of high quality that won’t disrupt your fasting program is to check the ingredient list and nutritional label for any sweeteners, carbs, amino acids, macronutrients, or other ingredients that can trigger an insulin spike.

You can use non-proteinogenic pre-workouts with zero calories, containing caffeine, creatine, and other natural pre-workout ingredients while intermittent fasting.

Also, it’d be wise to plan each gym exercise session outside your fasting window if possible.

Let us know about your opinion and experience with combining pre-workout supplementation and an intermittent fasting program.

Has this strategy helped you burn fat, get a great form, or reach any other workout goals?


References:

  1. https://www.cambridge.org/core/journals/british-journal-of-nutrition/article/sweettaste-receptors-lowenergy-sweeteners-glucose-absorption-and-insulin-release/FD76542E4E27715F92DD2B0BCF31483E
  2. https://www.scientificamerican.com/article/artificial-sweeteners-may-change-our-gut-bacteria-in-dangerous-ways/
  3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4990242/
  4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3772345/
  5. https://pubmed.ncbi.nlm.nih.gov/21512300/
  6. https://www.thieme-connect.com/products/ejournals/abstract/10.1055/s-2007-1021049
  7. https://pubmed.ncbi.nlm.nih.gov/23299767/
  8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2048496/
  9. https://pubmed.ncbi.nlm.nih.gov/15562223/

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