Fasted Running: Is Intermittent Fasting Good For Running?

Natalie Cecconi
Written by
Last update:

Is Intermittent Fasting Good for Runners?

There’s a growing body of scientific evidence that suggests that intermittent fasting may help individuals lose body fat and improve body composition. Recently, intermittent fasting has gained popularity in the running community, and many runners have reported positive results with this weight loss strategy.

However, there are some concerns about it such as burning muscle instead of fat, not allowing your body enough time to recover, and that all runners are built differently, meaning that some runners may not be able to workout and perform as well when intermittent fasting.

In this guide we’ll dive into what intermittent fasting is and whether or not it’s good for runners.

So, What is Intermittent Fasting?

Intermittent fasting is an eating pattern where you cycle between periods of eating and fasting.

Some intermittent fasting protocols encourage a 16 to 24 hour fast. Some people opt to extend the fasting period up to 48 hours.

Most intermittent fasting protocols involve alternating between fasting and periods of normal eating.

Some of the most common intermittent fasting protocols include:

The 16 to 8 Protocol: Eating normally for 16 hours and fast for the next 8 hours (usually overnight)

Eat-Stop-Eat: The first meal of the day is eaten in the afternoon. The next day, eat breakfast as usual. Then skip meals for 24 hours.

Why Running While Fasting Is Not Ideal

With the popularity of intermittent fasting (IF) increasing rapidly in recent years, you may be tempted to use your fasting window to run. After all, running on an empty stomach may burn more fat and boost your stamina.

But is that true and can you run while fasting?

I am not saying it is impossible, but I will strongly suggest to not try this while fasting.

I understand that some of you can be very tempted to test if fasting running works because fasting has certain advantages such as causing a slower blood flow in the body, reducing inflammation, giving your digestive system a rest and has been linked to a slimmer waistline. While these are all great things, it does not mean that it will be right for your running.

Lets break it down to understand why that is the case. First, running while fasting or even while in a fasting state can lead to a low blood sugar. As a result, your body will then attempt to break down fat stored in your muscles to provide energy for your muscles. In this condition, it is best to save your muscle instead of burning them and go for a light jog instead.

How Can I Get Into Running While Fasting?

Running is a great mode of exercise to lose weight and shape your body. Running is not just confined to the treadmill. You can lose weight by running outdoors as well.

Most people don’t realize that when you’re running, you go through a few different stages. The first part of your run is your warm-up and the last part is your cool down. In totality, your body will go through four stages:

Warm-Up Stage: During the warm-up stage, your body temperature is raised, your blood flow is increased, and your muscle elasticity is improved.

During the warm-up stage, your body temperature is raised, your blood flow is increased, and your muscle elasticity is improved. Elimination Stage: During this phase of your run, a lot of waste is eliminated, especially in the form of lactic acid. It is believed that it is waste that is responsible for soreness and any other aches and pains you feel.

During this phase of your run, a lot of waste is eliminated, especially in the form of lactic acid. It is believed that it is waste that is responsible for soreness and any other aches and pains you feel. Aerobic Stage: During these few minutes, the main source of energy used is from the aerobic system.

During these few minutes, the main source of energy used is from the aerobic system.

How Long and Fast Can I Run Fasted?

Is it Healthy?

Some proponents of intermittent fasting use it as a way to span the gap between breakfast and lunch or dinner. Others practice intermittent fasting as a way to maintain a desirable body weight.

However, what is less clear is whether or not running while in a fasted state is safe or advisable, and whether or not it leads to better performance or body composition.

In fact, most sports nutritionists will advise against it. This is because fasting will lead to a number of suboptimal results, such as:


On a cellular level, water is the medium for a majority of metabolic processes. Water transports nutrients to and from cells, and water regulates body temperatures and helps lubricate joints.

Without adequate water intake, dehydration will occur.

If you’re exercising for at least a couple of hours, you will need to rehydrate.

For a better breakdown of the role of water for the body, check out these two in-depth articles:

Science of Hydration

How Much Water Do We Need?

Reduced Mitochondrial Efficiency

Mitochondria are the powerhouses of the cell. They make energy by using oxygen.

They also help with many other important processes, including cell maintenance and repair. During fasting, the number of mitochondria will drop which can lead to a drop in cell energy production.

Are There Alternatives If I Want to Do Long or Intense Runs?

Longer or faster runs require more fuel. So if you want to run for more time at the same intensity, you’ll have to eat more during the run. The best scenario would be to consume energy gels. You can take them halfway through your run and keep eating them throughout, but keep it moderate or you’ll easily get glycogen-overload and cramps.

Some people prefer taking energy drinks instead to preserve their water balance, but that depends on your personal preferences.

As for the faster/higher intensity runs, you’ll need to consume more carbohydrates because your body will tap into glycogen, not fat.

Aim to refuel before and after you hit the road. Start with an easily digestible meal 3-4 hours before your run and consume a carb-rich meal (more than 400 calories) within 30 minutes of completing your run.

We hope this article gives you a better understanding of how can you compose and play shuffleboard dimensions.

How Long Can I Fast and Run Every Day?

Short term fasting is a form of occasional fasting that is not harmful for your body. You do this by simply supplementing your meals with high quality protein shakes the day before and a day after the fasting period.

Short term fasting doesn’t lead to a large weight loss. It is a good way to lose a few extra pounds, but not recommended for people who need to lose a lot of weight.

However, intermittent fasting and long term fasting could be detrimental to your hard earned training. Your body is very adaptive when it comes to training. That is why every time you push it hard, your body adapts and you have to push yourself harder to keep training results going. Long term fasting forces your body to adapt in a way that is not very beneficial for your hard earned training results.

If you decided to fast, then it is better to do it in a very short duration. Fasting for 24 hours should not have any long term negative effects on your training.

Anything Else I Should Know?

Not really. Fasted running is simple. You wake up in the morning, eat breakfast and then head out for a run. That’s it.

To quote Ben Greenfield, “The great thing about intermittent fasting is if you swing it in a way where you can eat your meals within an eight hour window and you backload a lot of your calories, you can eat large meals and still lose fat.”

I’ve found this to be true. For instance, instead of eating three meals a day, I’ve been spreading my protein meals into six smaller ones. One just after working out, two in the morning, around mid-morning and mid-afternoon, and then another two in the evening. I’ve also been eating large dinners, which allow me to go fasted for about 16 hours a day. So I’m technically fasting for 16 hours every day and eating for 8 hours.

Now you may ask, why not go with a stricter fasting protocol where you only eat for 2-4 hours a day? Well, I don’t have the willpower for it.

The take-home point is to manipulate your food intake times and incorporate more fasting into your schedule. All without restricting your calorie intake too much.


Breakfast is generally the heartiest meal of the day. Most people start their eating with breakfast and then move on to lunch, snacks and dinner.

While multiple studies show that a nutritious breakfast is important for optimal health, that’s not exactly what we will look at. What we’re concerned about here is the effect a full stomach has on running performance.

Does it hinder, or is it beneficial?

Here’s what we found.

Less Is More

Scientific research and expert opinions suggest that it’s better to eat a light breakfast than a heavy one. Runners who prioritized nutrition found that they were better able to keep their blood sugar levels stable, which is key for optimal running performance and fuel.

Chris McCormack, a multi-time Ironman Champion, also agrees with this sentiment. In an interview, he stressed the importance of keeping his body light and focused on the upcoming race, not what he would do after crossing the finish line.

Less is more when it comes to breakfast, especially if you’re running right after eating.


& Performance: Intermittent Fasting & Running

Intermittent fasting is a natural training style that can be quite challenging for beginners. I used to practice intermittent fasting in the summer and winter months, and today, I’m going to share my experiences and thoughts on intermittent fasting for running in this post.

Firstly, it’s important to know that there are many variations of intermittent fasting.

The majority of research on intermittent fasting has been done on one specific group of practitioners: people who fast for religious reasons. The lore on intermittent fasting for runners is based on this group of people.

As a result, if you’re planning to start an intermittent fasting regime, you should be aware that the guidelines formulated for religious people are very different from those formulated for athletes.

The intermittent fasting for athletes group has not been studied in depth yet, so there aren’t any specific guidelines. If you’re an athlete or an exercise enthusiast, research shows positive outcomes from intermittent fasting [1].

This research seems pretty promising, but how does this work with training? Does intermittent fasting help or hinder running? Can you use it or at least get something out of it or is it, in fact, counterproductive?

Well, let’s take a look at practice and a few details on the subject.


Tea, chocolate … and fasting?

Ever felt like you are being torn in different direction, simultaneously trying to do everything, all at the same time? How would you like it, if you could squeeze some extra time into the day without losing any of the options?

There is a way to do that! It could really be as simple as regulating your eating patterns. Intermittent fasting is a simple routine where you just give your body a break from eating for a while.

At its core, intermittent fasting is nothing more than an eating pattern you impose on yourself. In professional terms, it is also known as caloric restriction and not eating or caloric cycling. However, what really matters to you is that it will allow you to deduct without taking away … in other words, gain more without the extra effort.

Instead of eating the regular amount of meals, you just reduce the frequency of your routine eating to anywhere between one to three meals a day.

This is a natural pattern that your body has been following for millions of years. In fact, humans used to fast before they even knew what eating was. For millions of years, before the agricultural age, humans fasted whenever they were hungry.

Final Thoughts

If all this makes sense to you and you’ve read and digested the information here, intermittent fasting for runners could be really beneficial.

However, to get the full benefits, I’d recommend that you restrict your fasting periods to no more than 18 hours, maybe less for women.

This will help you get the most out of intermittent fasting, without unduly stressing your adrenals.

You can either fast 18 hours between dinner and breakfast, or you can fast 12 hours between supper and lunch. Or you can use an eating window that fits your schedule.

Just don’t leave it open longer than 18 hours and don’t overdo it. Remember, this is a marathon not a sprint.