Does pre-workout break a fast? — Explained by Simple

Written by Aly Owen

Medically reviewed by Louise Bula, RD

Published on January 26, 2024 | Updated on June 14, 2024

Looking to level up your workout beast mode? You may have heard of pre-workout supplements. 

But does pre-workout break a fast? Or does pre-workout break your fast? 

Here’s what you need to know about pre-workout and intermittent fasting. 

Will pre-workout break a fast? 

Let’s start with the frustrating news: there’s no universal answer to “Do pre-workouts break a fast?” because pre-workouts aren’t universal substances. Each one contains a blend of different ingredients, and what (and how much) is in that blend determines if you can take pre-workout while fasting. 

Generally, if a serving of pre-workout contains more than 10 calories, it could break your fast. 

But now the good news: “Will pre-workout break my fast?” also depends on your fasting goals. For instance, if you’re fasting for weight loss or metabolic health, having more oomph for your workout may be more beneficial to your goals in the long run. 

That’s why we always advocate for speaking with your doctor — everyone’s fasting needs and responses are different. 

We can also help you figure out and stay on track with your plan. Browse our guides on intermittent fasting and working out and what breaks a fast, or take our Simple quiz for more personalized recommendations. 

What is pre-workout? 

Pre-workout is a multi-ingredient supplement designed to improve athletic performance by boosting energy levels, muscle endurance, blood flow,[1] and cognitive function while reducing fatigue and muscle recovery time. 

During intermittent fasting, pre-workout may be used ahead of exercise to support fat-burning or weight-loss goals. 

Nutritional value 

Every pre-workout involves a different mix of ingredients, but they generally feature a foundation of:

• caffeine
• amino acids (especially creatine, l-theanine, l-citrulline, tyrosine, taurine, and beta-alanine)
• vitamins and minerals (like iron, magnesium, and phosphorus) 
• additive flavors like sugar and artificial sweeteners 

Since the ingredients of each pre-workout differ, so too does the nutritional value.[2] On average, pre-workouts contain anywhere from 10 to 70 calories per serving (most of which come from amino acids — protein building blocks — and sweeteners). 

Health benefits and possible drawbacks of using pre-workout while intermittent fasting

Whether or not you can drink pre-workout while fasting, do you want to? 

Think of pre-workout for intermittent fasting like a power-up in a video game: it may provide temporary boosts in performance that support your workout (and fasting) goals.

The typical combination of caffeine, amino acids, and nutrients in pre-workouts has the potential to supercharge: 

• energy [3]
• performance during endurance, power, and resistance training [4]
• muscular endurance and repair [5,6]
• injury prevention [7]

However, some of the ingredients in pre-workouts (namely caffeine) may not be safe for people who: 

• have existing blood pressure concerns or caffeine sensitivities; or 
• are pregnant, breastfeeding, or trying to conceive. 

Likewise, existing research is limited in its assessment of the longer-term effects of both pre-workouts and consuming pre-workouts during fasting.[1] More studies are needed to understand the impact of the different ingredients on different elements of health and well-being. 

Tips on using pre-workout during a fast 

Here are our simple tips for getting the best results with pre-workout while fasting. 

1. Consult your doctor. Pre-workouts aren’t right for everyone, and you don’t necessarily need one to achieve fitness or fasting results. Plus, fasting in general isn’t intended for everyone, so you always want to check if intermittent fasting is safe for you. If it is, talk to your healthcare provider to figure out the answer to “Can I drink pre-workout while fasting?” before mixing intermittent fasting and supplements.
2. Check the ingredient labels and serving sizes. Pre-workouts are a hodgepodge of ingredients, so make sure you know exactly what you’re getting. If you’re looking for a pre-workout that won’t break a fast, aim for one with less than 10 calories / serving. Likewise, if you’re concerned about intermittent fasting and insulin sensitivity or intermittent fasting and blood sugar levels, you may want to be wary of added sugars. You can also read our guide on what you can drink while fasting for guaranteed fasting-safe drink options.
3. Take your pre-workout during eating windows. You’ll eliminate both the calorie and “does pre-workout break intermittent fasting” concerns and likely have more energy. 
4. Pack your eating windows with nutrient-dense foods. You may not even need pre-workout for energy and performance enhancement if you’re getting premium fuel. Check out our guide on what to eat during intermittent fasting for inspo.

Written by Aly Owen

Medically reviewed by Louise Bula, RD

Published on | Updated on June 14, 2024