Should I Run Before or After Breakfast? (According to Science)

You’re finding tricks to fast-track your fat loss when you came across this popular advice “run on an empty stomach”. You’re not sure whether you should try it or not so you research. While doing your research, you noticed that the ideas are conflicting making you even more confused. So, should you run before or after breakfast?

Evidence suggests that running before breakfast, also known as “fasted cardio”, is not superior for fat loss. Other factors may affect the overall results such as the energy and performance during the exercise when fasted. Therefore, whether you run before or after breakfast should be based on your personal preference. 

Ahead, we will go deeper into running on an empty stomach aka “fasted cardio” and the pieces of evidence that supports and debunks it. We will also look at some advantages and disadvantages of fasted cardio. At the end of this article, I will give you my personal advice on whether you should run before or after eating breakfast. 

What Is “Fasted Cardio”?

Simply put, “fasted cardio” is an aerobic exercise done when your body is in a fasted state. In other words, running, biking, rowing, etc. on an empty stomach, typically before breakfast. 

When your body is in a fasted state, your insulin levels are low and your glycogen levels are depleted. Therefore, your body is forced to use fat as its fuel source. 

Fans of fasted cardio believe that it accelerates fat loss and improves body composition because you use it as energy. That is why bodybuilders, physique athletes, and those who’re attempting to achieve a summer body run in a fasted state. 

This method was popularized in the book Body for Life written by Bill Philips.

Off-topic: I usually run while listening to audiobooks and podcasts. It allows me to learn while I’m squeezing in a workout. If you want to try listening to audiobooks while running, you can sign up for Audible’s 30-day FREE TRIAL. You can cancel anytime at zero cost.

What Does Science Say About Running Before Breakfast?

In a 2015 study, 10 young, non-obese men performed 60 mins of aerobic exercise before breakfast, after lunch, or after dinner. Researchers found that only running before breakfast (in a fasted state) resulted in a greater 24 hours of fat oxidation. 

A similar study conducted in 2017 on 9 young females resulted in the same conclusion. 

These researches were performed on a relatively low population and both were performed by the same organization. There are also other conflicting researches regarding this topic. 

Some argue that fat loss shouldn’t be measured in hours but days and weeks. The rationale is that the body has the ability to adapt quickly to energy sources, therefore, reducing the amount of fat burned over time as your body adapts. 

In addition, a general rule in exercise science states that when you burn more carbohydrates, you will burn more fat post-exercise and vice versa. This is known as the “afterburn effect”. 

Intensity also plays a major part in the argument. It is a fact that the more intense your workout, the more calories you burn. Running in a fasted state may affect your performance, therefore, reducing the intensity and calories burned. 

2011 journal published by Brad Schoenfeld discussed the literature on fasted cardio and concluded that the literature does not support the effectiveness of fasted cardio. He added that the method may even have detrimental effects on muscle hypertrophy and strength due to increase proteolysis. 

2018 study aimed to look at the effects of ingesting protein before moderate-intensity treadmill exercise. They concluded that ingesting protein before fasted exercise yields the most increase in fat oxidation (Vs carbohydrates and fasting). They added that fasting has not led to more fat oxidization when compared with both carbohydrates and protein. 

That said, according to their research, the best meal before moderate-intensity exercise for better fat oxidation is a protein-rich meal. But even carbohydrates will yield better fat oxidation than running in a fasted state. 

Advantages of Running Before Breakfast

There are some people who decide to run before breakfast for different reasons. Here are some advantages of running on before breakfast

You’ll Feel “Lighter”

A lot of runners practice running on an empty stomach because they feel “lighter”. Ingesting food before a run may make you feel bloated and uncomfortable. 

You’ll Feel More Alert

When you’re in a fasted state, your body is put on high alert. This is rooted deep in human nature. Hunger means we need to hunt food, so blood will be available for our muscles to use and our heart beats faster to prepare ourselves for the “hunt”. 

Today, we may not need to hunt, but the same physiologic apply which we can use to our advantage when working out. 

No Time Wasters

Want to get over with your workout first thing in the morning? Run before breakfast. This way, you eliminate the time wasted preparing food and digesting your food. Plus, a nice meal feels better when earned. 

Less Chance of Stomach Problem

Have you ever tried having an upset stomach mid-run? Not so good, is it? By running before breakfast, there’s a lesser chance that you’ll be having an upset stomach in the middle of your run.

Disadvantages of Running Before Breakfast

Although running before breakfast is practiced by a lot of runners worldwide, there are still some disadvantages to it. Here are some of them.

Your Training Intensity Goes Down

High-intensity workouts require glycogen. Since your body is glycogen depleted, high-intensity exercises may feel harder to accomplish. This can also result in a decrease in calories burned. 

May Affect Strength and Hypertrophy

2015 study found that exercising in a fasted state increases cortisol levels higher. Cortisol is associated with protein breakdown in muscle cells which can result in weakness and muscle loss. Therefore, exercising in a fasted state may negatively affect strength and hypertrophy.

You May Feel Dizzy

An intense bout of exercise before a meal may cause dizziness for some, especially for individuals taking medications for diabetes. 

Ineffective For Improving Body Composition

Although some studies suggest that running on an empty stomach resulted in higher fat oxidation during the exercises, this does not relatively mean better “fat loss” in the long term. 

As mentioned above, intensity plays a major part in fat loss. Studies show that high-intensity exercises are superior in fat oxidation post exercises. Without glycogen, the level of intensity decreases, therefore, reducing your ability to tap into this “afterburn effect”. 

Is Running Before Breakfast Safe?

Yes, running at low to moderate intensity before you even have breakfast is safe for most healthy individuals. However, individuals with health problems such as diabetes must consult with their doctor before engaging in fasted cardio. 

Also, doing high-intensity running or long-distance running may result in dehydration or hypoglycemia. You want to keep the intensity low to moderate if you decide to run on an empty stomach. 

So, Should You Run Before or After Breakfast?

If you’re running before breakfast because you want to squeeze your workout in first thing in the morning, you want to “feel light” or you want to run when the sunlight is not yet so harsh, then yes you should run before eating breakfast. 

But if your reason is to lose weight faster, running after breakfast is just as good or even better than running on an empty stomach. 

It may also depend on the type of exercise you’re doing. You can go on an empty stomach with low to moderate intensity exercises but you’ll only be able to perform best on high intensity and long duration exercises following a high-carbohydrate meal. 

My advice is to experiment on the amount and type of food you intake before a morning run. Some of you may prefer to go on an empty stomach, others may need a slice of bread and coffee before they hit the pavement, while the others eat a piece of banana before they run and have breakfast after running. 

Whether you run with or without breakfast shouldn’t be the biggest of your concern if your thinking to maximize fat loss. Instead, focus on what allows you to perform at your best. 

Nicho Mauricio

Running wasn't always my favorite sport. I was a CrossFit athlete and I loved every bit of it. But since the pandemic began, I was forced to stay away from the gym and train at home instead. Things got boring. That's when I decided to trail run with my friends. I instantly got hooked. So I started training and researching all things running. As a beginner, I want to buy only the best running gear and do only the best practices. This blog is where I share what I've learned in my journey and my experiences as a runner.

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