Running On An Empty Stomach: Will I Lose Muscle Mass?

I’ve been running on an empty stomach for consecutive days when a friend warned me that it may reduce my muscle mass. Fear struck me so researched the facts on this matter.

As a general rule, people who run on an empty stomach will not lose muscle mass. Your body will have to deplete your glycogen stores and fats before it will start breaking down muscle protein for fuel. Most runners would’ve already stopped running before they even get to that point. 

Ahead, we will discuss more how your body uses fuel from carbohydrates and fats. We will also talk about why it is almost impossible to get to the point that you’re “burning” muscles.

Why You Won’t Lose Muscle Mass By Running On Empty Stomach

As someone who’s been going to the gym for the past 12 years (as of 2021), anything that reduces muscle mass usually raises my eyebrows.

I’m pretty sure you feel the same way too. We’ve worked incredibly hard only to find out that something can take your muscle mass away from you.

So imagine my surprise when my friend told me running on an empty stomach can burn my muscle mass. All my runs for the past 2 years have been on an empty stomach (I usually run early in the morning).

Frankly, I could’ve used my common sense. I’ve been running 3-5 miles at least 5 times a week on an empty stomach and my muscles are still there.

So when I went a little in-depth with my research as to how our body uses energy (And I have a background with this topic, I graduated as a physical therapist) I realized it’s going to be so hard to get to the point where you’re actually burning muscles.

Your body’s primary source of energy is the glycogen stored in your muscles. It takes a long time before it gets depleted (and yes, even when fasted). It will take around 90 mins of low to moderate-intensity exercise to get to the switchover point.

For an average runner, that’s around 7-10 miles before you even get to the point where you’re using fats for fuel. And I guess most of us can agree that intermediate runners like us rarely get to the 7-10 miles in a day unless it’s an event.

Is there any possibility that you’ll lose muscle when running? Yes, if you can endure running an ultramarathon distance without eating before and during your run. Not to mention, endure running when you’re already feeling dizzy.

Unless you’re that crazy, then you’re fine.

Why Do Runners Have Less Muscle Mass Then?

You must be wondering why do most runners have very little muscle mass then? That may have led you to believe that running on an empty stomach indeed burns muscle. But that’s actually not the case.

Runners, especially elite runners, spend most of their workout time running. Most of them rarely ever do resistance exercises. You and I both know that resistance exercises are the most effective way to stimulate muscle hypertrophy.

(Side note: I just want to point out that a 2015 study found that aerobic exercise such as running can in fact promote skeletal muscle hypertrophy in sedentary individuals. They even went on and promoted aerobic exercise as a way to prevent muscle loss in aging individuals.)

That’s why most of them are skinny. Not because running made them skinny but because they rarely spend time making their muscles big through resistance exercises. Add that to the fact that they burn a tremendous amount of calories each day.

To prove that it’s entirely possible to have huge muscles while still running long distances, let’s take a look at these famous athletes.

This is David Goggins, famous for his tough mentality and back to back to back 100-mile races under his belt. Despite his high weekly mileage, he still looks muscular. It’s also worth pointing out that he has an incredible work ethic and that he does strength workouts often.

Nick bare is one of the few people who was able to run a marathon in under 3-hours. And despite the fact that doing that feat involves lots of running, Nick Bare was still able to maintain his impressive physique.

If you’re interested in why marathon runners are skinny, I actually made an article focused on that topic. I highly recommend you check it out.

How To Make Sure You Don’t Lose Muscle When Running

If you want to be extra sure that you won’t ever lose muscle by running, you can do these good practices:

1. Eat Or Drink Carbs After Each Run

In general, it’s good practice to have a post-workout meal that consists of mostly carbohydrates.

When you work out (any kind of workout), you deplete your muscle glycogen stores. Glycogen comes from carbohydrates. So the only way to replace your glycogen stores is by taking in carbs.

Although it’s also best to take it from healthy sources such as bananas, other sources such as chocolate milk and orange juice work too.

2. Do Resistance Exercise Too

Even though running is an excellent form of exercise, having a well-balanced fitness program should still be your top priority.

That means you should never forget to include whole-body resistance exercises in your program. It could be in the form of bodyweight exercises or with weights.

3. Eat More If You Workout More

Say you signed up for a marathon training plan, it’s almost guaranteed that you’ll burn more calories than you would if you just did your regular daily run.

If so, you should increase your calorie intake to match your calorie expenditure.

4. Have a Balanced Diet

If you have a well-balanced diet, running on an empty stomach shouldn’t really be a big deal.

Final Thoughts

If the fear of losing muscle is preventing you from going after that early morning run, don’t worry! It’s very unlikely that you will lose muscle mass because of that.

If you really want to be certain, I suggest you eat something tolerable before you run (like a piece of banana). But really, it’s just for your peace of mind.

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.

Recent Posts