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Fasted Running: Is Intermittent Fasting Good For Running?

Intermittent fasting is all the rage in health circles these days. Since discussions of running nutrition focus so much on fueling properly and getting the right nutrients at the right time, you may be curious if fasting can work with running. We’ll cover that question, as well as pros and cons of running during intermittent fasting.

As with most things about running, whether or not intermittent fasting is beneficial depends on your goals and your personal makeup.

You’ll have to decide what’s best for you. By the end of this article, you should have enough information to make that decision.

Is Intermittent Fasting Good for Runners?

Intermittent fasting just means that you go without food for particular periods of time. It can be very long, like a multi-day water fast, or it can be shorter like 10-12 hours, most of which occur when you’re sleeping.

Intermittent fasting originally came about as an idea because nowadays, people eat food all throughout the day and don’t give their stomachs a chance to rest. Rather than eating anytime through the day, it’s better to have scheduled meals with clear breaks from eating.

That being said, running and intermittent fasting can work very well for some people. For example, you can burn fat faster because you aren’t burning the calories that you just ate. If you struggle with stomach issues, running fasted will be more comfortable for you.

You’ll also have better insulin levels, which can help prevent Type 2 diabetes by decreasing blood sugar levels. Not only will you get the benefits of a cardio workout, but you’ll also get the health benefits from being intentional about scheduling your meals.

If you’re trying to lose weight, cut back on your eating, or just have a sensitive stomach, intermittent fasting can help you as a runner and as an individual.

Why Running While Fasting Is Not Ideal

You might not want to incorporate intermittent fasting and running if you love to do speedwork or if you’re a long distance runner. The reason is that you can’t stress your body when it’s coming back from a fast, even if it’s just overnight.

Your body needs to have something in its system to have the energy it needs to do a hard workout, whether that’s intervals or a fast, intense run.

Similarly, you can’t do a several-hour long run on a fasted body. Your body needs fuel to make it through.

Combining fasting and stress just doesn’t work, and you could be compromising your immune system. You might even make yourself more susceptible to putting on some belly fat if you’re fasting and trying to do hard, stressful workouts.

Finally, fasted running can, in extreme cases, cause a decrease in muscle mass. If your body doesn’t have enough stores of calories to draw on, it can start eating muscle.

In order to be lean and mean, you need to make sure that your body has enough fuel to run.

How Can I Get Into Running While Fasting?

If you think that you’d like to start eating more intentionally and begin intermittent fasting – while also still keep running – you need to be strategic. You’ll need to build up your distance slowly and carefully.

Even if you have been running regularly and for fairly long distances, when you add in fasting, you’ll want to approach running as if you’re just getting into it again.

Start with short, easy runs of no more than three miles, and see how your body handles that with intermittent fasting.

You should start with a 10-12 hour fast and increase slowly to whatever range you’re trying to reach. Then adapt your distances as needed. This means that you should eat dinner and then make sure it’s been 12 hours before you eat breakfast.

Finally, you need to schedule your meals around your runs. In other words, your body has consumed carbs, protein, and other nutrients during a run, so you need to make sure that you eat soon thereafter to replenish your food stores.

This means that you can’t set up a schedule of only eating between 11am and 5pm and then go for a run at 5am. Or vice versa: Don’t go for a run at 5pm and then not be able to eat until the next morning for breakfast.

How Long and Fast Can I Run Fasted?

As we mentioned above, you can’t expect to do a long or hard workout when you’re in a fasted state. Instead, you’ll probably be looking at 5k-10k runs at 65% of your maximum pace. That means if your max pace is a 6:00/mile, you’re looking at running at 10:00 minute mile.

If you feel good and have good energy levels throughout the day, you can increase your distance and pace. But you want to make sure that you don’t overdo it. Running on a fasted state leaves you little margin for error.

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

If you like the idea of intermittent fasting but you still want to be able to do long runs or intense runs, then you can alternate fasting and training days. On the fasting days, you’ll do really easy runs. On the training days, you can do an intense and/or long run.

This set-up has the added benefit of encouraging your body to rest and recover on the off days, and doing what running experts suggest: do your slow runs really slow! You will have to keep track, though, what day is a fasting day and what day is a training day.

How Long Can I Fast and Run Every Day?

As long as you feel good and maintain good energy levels throughout the day, you can fast and run every day. Keep track also of whether you are getting sick more than usual, or if you feel fatigued. These are your body’s signs that it is getting overtaxed. When you do eat, make sure that you’re eating quality foods.

Again: listen to your body. If it’s just too much to do intermittent fasting and run, figure out a middle ground that works better. Maybe it’s cutting out the snack before you go to bed. That alone can make a huge difference.

Anything Else I Should Know?

One of the best things you can do for an intermittent fast is to eat a large breakfast, a medium sized lunch, and a small dinner. You should be eating the most food when you need the most energy.


As they say, breakfast is the most important meal of the day. You should definitely treat it that way when you’re figuring out the schedule for your intermittent fasting. If you like to run in the morning, eat something small like half a banana before your run. Save the big breakfast for afterward.


Another thing that is incredibly important is making sure that you’re getting plenty of sleep. Most people already don’t get the 7 to 9 hours of sleep that’s recommended. Hitting those numbers is key for intermittent fasting.

In fact, you’ll actually need more sleep because your body isn’t going to have as much food in it. On average, you should try to have at least 30 to 60 minutes more sleep per night. Instead of eating that sugary snack at 9:30, go to bed and get up at 6 for your run.


Finally, avoid coffee on an empty stomach. Your body needs to have 10 to 12 hours with nothing but water to get the full benefits of fasting.

Coffee will completely negate this by affecting your liver and releasing fatty acids. Eat breakfast first.

Final Thoughts

If intermittent fasting still sounds interesting to you, ease into it slowly and see how it feels. It is okay to realize after a couple days that it just won’t be a good fit for you.

That being said, remember that a lot of things can be adjusted. You can change how long you fast, how far you run, when you eat your meals, what kind of food you eat, how much sleep you get, and so forth. Feel free to play around and find what works for you.

If you’ve been trying for a longer period of time and constantly adjusting to suit your needs but nothing is working, it might be time to call it quits and try another diet or eating habit instead.

Rachel Basinger
The Wired Runner