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Should You Take Pre-Workout On An Empty Stomach?
Good Or Bad?

Isaac Robertson
Published by Isaac Robertson
Fact checked by Donald Christman, BHSc FACT CHECKED
Last updated: April 13, 2021

The safety of taking pre-workout supplements on an empty stomach has been the subject of countless debates in the fitness world.

Many people say this practice causes no harm, while some warn against doing so.

To clear up the confusion, I pored through tons of scientific journals and articles to find out what the experts really say about it.

Here's what I learned.

Should You Workout On An Empty Stomach?

A female ready to start her workout

Before answering whether it's okay to take pre-workout on an empty stomach, we first need to ask ourselves: is working out on an empty stomach even advisable?

Science says it’s completely fine. In fact, working out on an empty stomach burns more fats.

When there is zero food caloric energy available, your body turns to stored fat to give you energy, helping you engage in a high-intensity workout even when you're in an overnight-fasted state.

However, doing so can also lead your body to burn muscle for fuel in addition to fat [1]. Although the percentage of muscles burned during this process is comparatively small, it can still be a roadblock to the success of any weight loss program.

Also, exercising on an empty stomach can lead to heightened muscle catabolism—also known as protein breakdown—and lethargy.

But, in general, training in a fasted state—with most of the fast occurring during sleep—will likely give you its fat-burning and weight loss benefits without totally depleting your energy during your workout.

How Taking Pre-Workout On An Empty Stomach Affects Your Body

Scoop of protein, bcaa and creatine, omega3 on a wooden table

Now onto the main question: Is it okay to take your pre-workout supplement on an empty stomach?

The answer is yes.

In fact, the only difference between taking pre-workouts first thing in the morning before breakfast rather than after a meal is the time it takes for them to take effect.

If you haven’t eaten anything before taking your pre-workout drink, chances are you will feel its effects much quicker.

Without food to slow its transit into the digestive system, your pre-workout will pass into your intestines faster, thereby accelerating the entry of its ingredients into your bloodstream.

If you recently had a meal, your pre-workout will still be effective at assisting your exercise performance during training. In this case, you should wait anywhere from 30 minutes to an hour before your gym session to feel its ingredients kicking in.

But if you’re still concerned about reducing the performance-enhancing benefits of a pre-workout supplement by taking it on a full stomach, here’s an idea—don’t eat any foods with a lot of fiber in them.

That means avoiding whole grains, nuts and seeds, raw fruit, raw vegetables, and the like [2].

And since we’re already on the subject of food, don’t forget that experts recommend that you eat meals rich with all 3 macronutrients (protein, fats, and carbs) after working out to recover faster [3].

Any Side Effects?

3D model of a pre workout supplements on a one scoop of spoon

Most pre-workouts are formulated so that when you take them on an empty stomach, they won’t cause any adverse reactions.

As I’ve mentioned, the only effect will be quicker absorption in the bloodstream.

However, there are a few potential side effects you should keep in mind.

Low blood sugar

If you have a blood sugar-related condition like hypoglycemia, your glucose level—which is your body's primary energy source—is lower than normal.

When a person with this condition goes for several hours without eating, they might end up feeling dizzy, weak, and nauseous. And if you take a pre-workout supplement on top of these symptoms, you'll definitely feel worse.

So if you're at risk of hypoglycemia, it's best to have a small snack before starting your workout session.

Digestive problems

Another possible side effect of taking a pre-workout drink on an empty stomach is digestive system irritation.

That’s because most pre-workouts contain artificial sweeteners, caffeine, and other stimulants known to cause gastric distress.

So if you’re someone with a sensitivity to synthetic sweeteners, caffeine, and other stimulants, you should eat before you take your pre-workout to prevent any stomach issues from happening.

Best Pre-Workout Ingredients For Training On An Empty Stomach

Pre workout powder container with dumb bells beside it

Although it’s generally safe to take pre-workout while fasting, not all ingredients in a pre-workout supplement are great on an empty stomach.

Here are the best pre-workout supplements to look for if you plan to include intermittent fasting or fasted training in your workout routine.

  • L-Citrulline + L-Glutathione

The key to achieving the coveted “muscle pump” is having healthy circulation. And for one to have healthy circulation, there must be sufficient nitric oxide (NO) in the body.

The L-citrulline + L-Glutathione combination promotes the synthesis of NO, a compound that relaxes blood vessels and increases blood flow.

L-citrulline also enhances muscle power and strength [4]. Although it is better at boosting NO than L-arginine supplements, this ingredient has poor bioavailability, making its standalone effectiveness questionable.

For this reason, L-citrulline must be paired with L-glutathione, one of the body's most potent antioxidants that seems to enhance the former’s bioavailability.

Without breaking your fast, these two substances may help support NO activity, improving your lean muscle growth and workout power at the gym [5].

  • Creatine

Creatine is an organic compound stored in muscle tissue as fuel for ATP energy production.

Creatine is a favorite among many fitness enthusiasts because it’s a natural method of improving workout strength, energy, and physical performance.

Although it doesn’t give the instant “feel good” effect of caffeine, the reason it’s so popular is the numerous benefits it provides.

Here are some of them:

  • Stimulates insulin-like growth factor 1, resulting in muscle growth, development, and recovery [6].
  • Replenishes ATP energy levels exhausted during high-intensity exercise, helping you sustain exercise endurance and improve your gym performance [7].
  • Buffers lactic acid within the muscles to help lengthen muscle exertion to failure, thereby enhancing workout endurance [8].
  • BCAAs (Branched-Chain Amino Acids)

The aminos that can best support lean muscle mass growth is BCAAs, amino acids known to boost protein synthesis while protecting your muscles against the protein-depleting effects of exercise.

BCAAs quickly absorb into the muscles and provide several performance-enhancing benefits:

  • Prolongs workout energy and endurance
  • Blocks neurotransmitters that cause fatigue
  • Stimulates insulin for improved amino acid uptake
  • Supports the synthesis of growth hormones in the body
  • Preserves lean muscle mass while diminishing soreness

You can take a BCAA supplement either before going to the gym or during exercise.

Why Did My Pre-Workout Stop Working?

When you start on a pre-workout, all its benefits are all brand new feelings.

But when you take the same pre-workout formula almost every day, your cellular receptors become saturated and your nerve endings get desensitized [9]. Both of these things can minimize the ability of a pre-workout to stimulate your nervous system.

“We sense this change very dramatically the first few times it happens, but then we become accustomed to the feeling, so subsequent uses of the very same product at the very same dose will feel ‘less’ in terms of magnitude of effect.”

 

- Shawn Talbott, Ph.D., L.D.N., Nutritional Biochemist

To prevent this “dulling sensation” you can either go off your pre-workouts for two to three days or switch to pre-workouts with a formula that gives energy using other ingredients.

Also Read: Is It Really Necessary to Cycle Pre-Workout?

Pre-Workout Supplements On An Empty Stomach: Final Thoughts

The choice of whether to take your pre-workout supplement first thing in the morning largely depends on your personal preference and current health condition.

If you want the effects of your pre-workout to kick in much faster, then you should take a pre-workout on an empty stomach.

But if you have digestive and blood sugar-related health conditions, it's best to first ask your doctor about the safety of taking this sports supplement without food before trying it. Otherwise, it's a generally harmless practice.

How has taking pre-workouts on an empty stomach worked for you? Let us know in the comments below!


References:

  1. https://www.sharp.com/health-news/should-you-work-out-on-an-empty-stomach.cfm
  2. https://www.bodybuilding.com/content/3-mistakes-youre-making-with-your-pre-workout-supplement.html
  3. https://www.healthline.com/nutrition/eat-after-workout
  4. https://pubmed.ncbi.nlm.nih.gov/10442090/
  5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4472409/
  6. https://pubmed.ncbi.nlm.nih.gov/18708688/
  7. https://pubmed.ncbi.nlm.nih.gov/12701817/
  8. https://pubmed.ncbi.nlm.nih.gov/23164647/
  9. https://www.mensjournal.com/food-drink/why-isnt-my-pre-workout-supplement-working-anymore/

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