Does pre-workout break a fast? (Complete guide)

Fasting has been making waves in the health and fitness scene, gaining a reputation as a promising approach to improving overall well-being. The essence of fasting revolves around alternating between periods of eating and abstaining from calorie intake. But here’s the twist: what about those of us who swear by pre-workout supplements to rev up our workouts? The burning question is, does pre-workout break a fast? In the journey ahead, we’ll navigate this intriguing topic, offering insights to help you make the most of your fasting and fitness routine.

What is a fast?

What is a fast?

Fasting is when you choose not to eat for a period, typically ranging from 12 to 24 hours. During this time, your body relies on stored energy instead of food for fuel. People fast for various reasons, such as weight management or potential health benefits.

The core idea behind fasting is that your body switches from using energy derived from food to tapping into its internal reserves, like sugar and fat. This metabolic shift triggers specific changes in your body that can have positive effects on your health.

Does pre-workout affect your fast?

Pre-workout supplements are designed to enhance performance, boost energy levels, and reduce fatigue. But the question often arises: does pre-workout break a fast? Let’s explore this by examining some common pre-workout ingredients and their potential impact on fasting.


Caffeine is a well-known ingredient for improving exercise performance, energy levels, and focus. Fortunately, caffeine itself doesn’t contain significant calories or nutrients that can break a fast. While some caffeinated beverages may influence digestion, pre-workout supplements usually contain pure caffeine, minimizing such effects, but if you still want to stay away from caffeine, there are low- or no-caffeine pre-workout options.

In summary, caffeine in a pre-workout is unlikely to break your fast.


Sugar, found as glucose or dextrose in some pre-workouts, provides quick energy during exercise. However, sugar contains calories and nutrients that can trigger an insulin response, potentially halting fasting benefits. While small carbohydrate servings (less than 50 kcal) likely won’t break a fast, it’s advisable to avoid sugar to maintain a fasting state.

Non-Calorie Sweeteners:

The impact of non-caloric sweeteners on fasting is not fully understood. Some studies suggest minimal effects on insulin secretion, but the overall significance is debated. These sweeteners have negligible calorie and carbohydrate content, and many intermittent fasters consume them without breaking their fast.

Amino Acids (BCAA/EAA):

Although protein and amino acids can cause insulin spikes and contain calories, typical pre-workout servings contain minimal amounts and are unlikely to break a fast. If precise control is desired, avoid amino acids in pre-workouts while fasting. Generally, if protein and carb totals remain below 50 kcal, you’re within the fasting range.


A common performance enhancer, creatine is calorie-free and doesn’t affect insulin response. Pre-workouts containing only creatine and no calorie-containing ingredients are considered safe during fasting.

Citrulline Malate:

Supplements with citrulline malate are suitable during intermittent fasting, as they delay muscle fatigue and improve strength, endurance, and recovery. Citrulline malate doesn’t trigger an insulin response, making it fasting-friendly.

Beta-Alanine, L-Theanine, and Betaine:

Non-essential amino acids like beta-alanine, L-theanine, and betaine typically don’t elicit significant insulin responses, making them safe for consumption during fasting periods. And if you ever wondered why your pre-workout makes you itch, it is beta-alanine.

In summary, most pre-workout ingredients are unlikely to break your fast, especially when consumed in moderation. However, it’s essential to consider individual tolerance and fasting goals, and consulting a healthcare provider can offer personalized guidance.

How Many Calories Are in Pre-Workouts?

Pre-workout supplements typically contain zero calories or an extremely negligible amount if they use artificial sweeteners and lack BCAAs (branched-chain amino acids). Vitamins and minerals, although essential nutrients, don’t contribute calories.

It’s important to note that while a pre-workout may claim to have zero calories, the presence of artificial sweeteners could still potentially trigger an insulin response, impacting the integrity of a true fast.

Will Pre-Workouts Break a Fast?

Does pre-workout break a fast

Assuming you haven’t consumed sugar or carbs and have fasted for at least 8 to 10 hours, a pre-workout likely won’t significantly impact your fasting goals. This is because your glucose and glycogen levels should be quite low, so even a pre-workout with a few calories won’t heavily affect your metabolism.

Moreover, if you plan to eat after your workout, the timing of your pre-workout consumption is towards the end of your fast, and any minor disruptions can be easily compensated for in your post-workout meal.

However, if your fasting objectives differ or you’re striving for a “true fast,” it’s best to avoid pre-workouts to avoid any chances of breaking your fast.

Why Pre-Workouts Can Be a Good Idea When Fasting?

Let’s talk about why using a pre-workout during fasting might actually be a smart move. The star player in many pre-workout supplements is caffeine, and it can do something pretty cool when you’re fasting—it helps your body burn fat for energy.

There was this study, and it found that caffeine can help your body use fat more effectively, especially when you’re doing things like running, biking, or even just taking a brisk walk. Even though the study focused on exercises like jogging and cycling, it tells us something important: when you’re fasting and have caffeine from a pre-workout, your body can tap into its fat stores more efficiently for fuel.

So, if you’re into fasting and do workouts like cardio on an empty stomach, caffeine in a pre-workout could give your fat-burning efforts a nice boost.

My Recommended Pre-Workout

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Whether pre-workouts break your fast or not depends on your fasting goals. If you’re fasting to shed pounds or boost your workout performance, a caffeine-based pre-workout might help burn fat during exercise. But if you’re fasting for other reasons or you are striving for a “true fast”, it’s safer to skip pre-workouts.

Remember, there’s no one-size-fits-all answer. Think about why you’re fasting and how your body reacts. When in doubt, chat with a healthcare professional or nutrition expert to pick the right path for you. Happy fasting and working out!

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