Benefits of Running on an Empty Stomach

Benefits of Running on an Empty Stomach

By Coach Adolfo Salgueiro

In a WhatsApp running group, one of our friends recently shared an article from Men’s Journal Magazine praising the benefits of training in a fasted state. The sub-title alone was promising: The Science-Backed Benefits of Running on Empty, by Spenser Mestel.

I opened it as I thought of how pseudo-science has affected even the most mundane, easy runs lately. Most come from unqualified social media influencers or studies commissioned by companies that will benefit from their results. Dr. Tim Noakes is famous for questioning Gatorade’s science-based recommendations about the benefits of consuming Gatorade. And like that, examples are plenty.

Running on an empty stomach
Running on empty has its scientifically proven benefits (Image by ChatGPT)

We tend to forget that humans have been running for thousands of years. Hunted gatherers did so for hours while chasing an animal until it collapsed. Yet, they were able to pick it up and take it home to feed their families. They didn’t carry water packs to replenish every drop of sweat. They didn’t carry chews or gels to replace every calorie they burned.

Sure, we have evolved in those thousands of years. The bushmen of the Kalahari were not used to spending their day under air conditioning, sitting in front of a computer, or wearing shoes before they went hunting. But we haven’t entered devolution either. Our bodies were built to withstand a certain level of dehydration and caloric deficit.

I want to leave no room for doubt that I am not advocating against electrolyte replenishment, chews, gels, or any other product. God knows I could not have finished my last few marathons without the help of Maurten gels. What I am advocating against is their overuse, to the point where our bodies become unable to learn how to use their own resources.

Running on an empty stomach is not a fad passed around by social media influencers. Based on the article in question and the study on which it was grounded, it is a well-rounded premise that “fasted cardio” and “low-glycogen” training are similar but distinct practices that can offer real metabolic advantages if done right.

Running on an empty stomach or fasting
While skipping breakfast can be beneficial, you don’t have to do it for every run (Photo Pexels)

Mestel brings in Professor Richard J. Bloomer, Dean of the College of Health Sciences at the University of Memphis, to clarify the lingo. According to him, a “fasted state” can simply mean not eating for 10–12 hours, like overnight. But low-glycogen training goes further. It implies depleting your muscle glycogen stores, typically by limiting carbs over a longer period. Both approaches can shift your body’s fuel source away from sugar and toward fat, especially during lower-intensity sessions.

According to the study, these are some of the benefits:

  • Fat Adaptation: By skipping that pre-run snack or breakfast, your body is nudged into burning fat for fuel. Studies cited in the article showed that both men and women increased fat oxidation after exercising in a fasted state. Simply put, you’re teaching your body to tap into a steadier, more abundant fuel source.
  • Less Stomach Drama: Fasted runs can reduce gastric discomfort for those with fussy guts. No food means nothing sloshing around in there. It’s a win for morning runners who’d rather not eat at 5:00 AM just to avoid bonking at 6:00.
  • Convenience: This one isn’t science; it’s life. Rolling out of bed, lacing up, and getting it done before breakfast is just easier sometimes.

The science goes even deeper. In a 2010 study from the Journal of Applied Physiology, Beneficial Metabolic Adaptations Due to Endurance Exercise Training in the Fasted State by Van Proeyen et al., this wasn’t anecdotal evidence; it was a tightly controlled experiment. Two groups trained identically on bikes for six weeks. One ate carbs before and during workouts; the other trained fasted.

The result? While both groups got fitter, the fasted group showed superior metabolic adaptations. Their muscles improved at burning fat, their ability to use stored fat (even deep in the muscle) improved, and they kept blood sugar stable over long workouts. The carb-fed group? They didn’t show those perks.

Conclusion

It is not about skipping breakfast forever or starting every workout on an empty stomach. But if you mix in a couple of easy runs each week without eating beforehand, especially when effort is low and stakes are even lower, your body might thank you. You’ll become more metabolically flexible, able to use fat when needed and carbs when it matters most.

Don’t go overboard. It’s about teaching your body to adapt so it can rise to the occasion, whether chasing a PR or just running for joy.

You can read the Men’s Journal article by clicking here.

Curious to try it? Leave a comment and let me know your experience. And don’t forget to subscribe to the Foultips.Run newsletter by clicking the button below.

To Fast or Not to Fast?

To Fast or Not to Fast?

By Coach Adolfo Salgueiro

It is an ongoing debate between runners, coaches, scientists and onlookers in general if we should run in a fasting state or not. Despite all the science, studies, anecdotal evidence and articles on the subject, the verdict boils down to a simple two-word answer: It depends.

Fasting

Figuring out what to eat and when is the responsibility of each runner.

It depends on what type of runner you are, how long you are running, when you’re going for a run, what are you trying to accomplish, and so many other factors. There are as many answers as there are runners. And what works for you doesn’t necessarily work for me.

If you run first thing in the morning, you can do a simple A/B testing and figure out what works for you. There are people that can’t function without a coffee and there are people that will have to rush behind the bushes if they have a coffee before running. You can try with an apple, or a banana, or a bagel, or toast, and from there find out what helps you out and what upsets your stomach. A running partner once told me she had a bowl of oatmeal before our long runs. If I had a bowl of oatmeal, I would be the one running for the bushes.

The key to this is not to overdo it. You are just looking to top off your glycogen stores before you hit the road. You are not taking breakfast. Digestion uses a lot of blood, same as running does. So when the body diverts the blood to fuel your running, digestion stops. The rest I will leave to your imagination.

Running on a fasting state, you will teach your body to use its own resources without depending on outside fueling. This is beneficial when you are training for a long effort, usually the half-marathon and above. As you your body adapts to the finite amount of glycogen it has available, it learns to use its stored fat as a source of fuel. This becomes invaluable when you go beyond the 18-20-mile mark, so you can avoid the dreaded wall.

I want to make absolutely clear that I am not saying to go run 18-20 miles just with what you woke up with. You should not neglect your fueling strategy (that is a topic beyond the scope of this blog post). What I am saying is that running in a fasting state will train your body to reach that critical point with something left in the tank.

Fasting

The time of the day in which you run is one of the key variables on fasting or not

The time of the day in which you run is key on deciding if fasting or not fasting is right for you. If you run in the afternoon, you shouldn’t be fasting all day. What you must do is adjust your eating habits so you can fulfill your training without interrupting digestion. Once again: A/B testing. You will have to discover what works best for you. You will have to eat something before your run, but what and when is the key. It could be some fruit, or a sandwich or handful of almonds; either two or three hours before your run. Or maybe its just one hour. It is your responsibility to figure that out.

Even if you prefer running in a fasting state, you must prepare for the task you will be facing. If you are running New York, or Boston, where you may be starting at 11AM, you can’t do it in a fasting state. You must eat something hearty for breakfast with enough time to digest (about 4 hours). You breakfast needs to be a low-waste meal so you can avoid number-2 unscheduled breaks. Astronauts for the first Mercury and Gemini missions, when bathrooms were not available in their spacecrafts, used to eat filet mignon, eggs and toast before launch. You may want to switch the filet mignon for another type of protein but in general, this is a great option. One that needs to be practiced before race day.

My recommendation is to start working on your A/B testing right away. Find the benefits and the drawbacks of fasting or not; of eating and eating what; of eating or not based on how long are you planning to go; on when to eat; on figuring out if coffee, oatmeal, fruit, toast or whatever, works best for you; or not. The time to work on this, is now, not when you are tapering for your marathon or the morning of your goal race.

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