Running On An Empty Stomach: What You Need to Know

One would think that running on an empty stomach–on little to no fuel–is illogical. One would think that it’s actually dangerous. 

But the truth is that you can safely and successfully run on an empty stomach. And in some cases, you might want to. 

The reasons may surprise you. 

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Defining “Empty Stomach”

Empty stomach means no food, of course, but that doesn’t preclude you from liquids. Especially in the case of empty stomach runs, keeping hydrated is a necessity. Water is the favorite, as it has no calories, but you can also drink black coffee, plain tea, or any refreshing beverage that’s as low-calorie as possible.

What Kind of Runs is Empty Stomach Running For?

It’s for low-to-moderate exertion runs that last 90 minutes or less. Heavy exertion over longer periods would be unsustainable. Dizziness, cramping, and muscle fatigue would make it impossible. That’s why keeping a little snack (like an energy bar or sports drink) with you during the run can be advantageous. Have it during the run or right after. Let your body tell you when it needs that little boost.

Empty Stomach Running and Fat

A lot of people think that by running on an empty stomach, the body would look to its fat reserves to fuel the run, accelerating weight loss. This is untrue. In 2014, Journal of the International Society of Sports Nutrition did a month-long study of two groups: aerobic exercisers who ate prior to their workout, and aerobic exercisers who fasted the night before. Results showed that there was no major difference in weight loss between the two groups.

Eating Without Eating

The body can be fooled. The mouth can trick the brain into thinking that we’ve eaten. By rinsing and spitting a carb or protein-heavy drink during your empty stomach run, the brain will believe the body is being fed.

While immediate digestion is impossible, the alert fools the body with the idea of a meal, allowing it to feel safe to spend some stored nutrients to keep the run going. You can even eat a sports bar during one of these runs and feel an immediate surge of energy again, extending your run. Sure, your body is aware that it can’t make use of the nutrients yet, but it believes that there’s a back-up on the way and that reserves can be used now since they’ll be replenished shortly.

Sure, it seems like teasing your body with fuel that isn’t coming seems a little untoward, but clearly, the body was holding out on us anyway with that secret reserve.

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Why People Run on an Empty Stomach (Benefits)

This sounds like doom and gloom, doesn’t it? Like we’re trying to talk you out of trying it. After all, you can’t increase your endurance or speed like you can with other running exercises. The benefits of empty stomach running are more internal. Some people don’t enjoy the feeling of food sloshing around inside them while they’re running. Admittedly, it can be uncomfortable and off-putting. Some even become nauseous. Empty stomach running cuts out the problem, though for some that empty, and fatigued feeling is also uncomfortable and off-putting. Either way, they’re both things that runners can simply adapt to, but go with whatever your preference is. I’m not here to judge.

As for the physical benefits–do you know that song “Don’t Know What You Got (Till It’s Gone)” by Cinderella? That’s the effect empty stomach running has on the body. It makes the body learn to use its muscle glycogen stores better. In other words, it makes your body more energy efficient. When the body sees what it can do without food, it will be more efficient with how it uses food when it has it.

The Drawbacks

You’re going to feel like crap, and not in a good way like you’re breaking through plateaus and making gains.

Empty stomach runners are prone to post-exercise oxygen consumption. This causes a washed out, exhausted feeling. The fact that you were already essentially running on fumes will increase the likelihood that you’ll overeat later in the day. Since empty stomach running doesn’t do much for weight loss, it’s possible that you can gain weight doing this, making all that pain and suffering for nothing.

Some people are into that, sure and good for them, but we doubt that it applies here.

Some Confusion About Gains and Losses

There is also an ongoing debate that should be noted. Some believe that the stress of empty stomach running forces the body to release cortisol into your system, which breaks down muscle into usable proteins. In other words, you’d be losing muscle strength by running on an empty stomach. Others claim that this is a myth. Those people believe that the body is actually burning through its muscle glycogen (glucose) stores. The glycogen is used as fuel during the empty stomach run, and the body will only actually break down muscles into proteins in extreme situations, where the runner has gone from a low to moderate run and is exerting themselves too much that not only will the glycogen reserves become depleted, but the body would then move to consume the muscles for protein. The lack of glycogen would also, of course, bring on symptoms of dizziness and fatigue.  

An Important Warning

While we’re on the topic of glycogen usage, we need to mention that empty stomach runs just aren’t a good idea for diabetics. The body’s insulin supply depletes overnight. Empty stomach runs require the sugar and glycogen stores. Diabetics are already at a dearth of insulin, making empty stomach runs an unnecessary danger. If you’re diabetic and considering an empty stomach run, speak to your doctor first.

Scheduling an Empty Stomach Run (Morning)

It’s easiest to schedule an empty stomach run for the early morning since that’s when your stomach will be at its most empty, along with the body’s glycogen supply. However, the work starts the night before. On days where you’re going to run on an empty stomach, have your dinner at 5:00 PM. Your dinner should be healthy if a little carb heavy since you can’t eat again for the rest of the night.

In the morning, it might be a gurgling, angry stomach that wakes you, but it also tells you that you’re at your optimal empty stomach level.

Scheduling an Empty Stomach Run (Afternoon and Evening)

Yeah, I’m not a morning person either. Not much of an afternoon person, if I’m being honest. Well, if you prefer to run a little later in the day, you can still do it on an empty stomach. You’ll need a six-hour difference between the run and your last meal. That will allow your blood sugar level to drop enough for the glycogen to be released to keep you stabilized. Again, that last meal should be a little carb heavy. However, a fruit smoothie or some greek yogurt with walnuts could see you through the six-hour difference. You’ll certainly be hungry by then in time for your run.  

Delaying Not Denying

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Running a relaxed pace should be fine if you follow this guideline, but it’s also important to remember that recovery is an important part of a runner’s regimen. Part of that recovery is replenishing your body of the nutrients–and in the particular case of empty stomach runners–the glycogen supply.

It’s easy to just want to plow through and get on the rest of your day. Go home, clean up, deal with the soul-crushing bureaucracy that stymies creative ingenuity out of fear of client reaction at work, and deal with the body’s lack of fuel until lunch.

This is a bad strategy. Not only will it only increase the aforementioned likelihood that you’ll overeat later in the day, but it will take your body much longer to recover after your run, even if it was at a more leisurely pace.  

Running on an empty stomach doesn’t mean skipping breakfast, just delaying it (and perhaps modifying it slightly).

You’ll still want something with a decent amount of carbs and a little bit of protein, but instead of a good runner’s breakfast of plain oatmeal with some fruit, or egg whites, you might opt for something more expedient. Slim-Fast (do they still make those?), Ensure, or some chocolate milk can be a good source of replenishment until lunch.

At lunch, resume your normal diet. Oats or peanut butter will help replenish your reserves and return your body to its feeling of normalcy. Hopefully, by running at the right pace and strategically parsing out nutrients your body can become more efficient, learning to get by with less and make more of what it has when it has it.


  1. Chicago Tribune
  2. Telegraph
  3. Runtastic
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