How To Run Without Losing Muscle Mass + 10 Effective Ways To Do So

Running is an excellent way to strengthen your heart and lungs, increase bone density, improve your mental health, and reduce your blood pressure, among many other benefits

Running is also a very efficient way to burn calories, which is why many people turn to running to help them lose weight. However, depending on your metabolism, body composition, and weight goals, it can be hard to do as much running as you’d like without losing muscle.

Moreover, even if you are trying to lose weight by running, you likely want to lose fat, not muscle, so many runners want to know how to run without losing muscle mass, or ask themselves, how much should I run to not lose muscle.

In this guide, we will discuss how to run without losing muscle mass and how to enjoy running while working towards your body composition goals in a healthy and sustainable manner.

We will cover: 

  • Does Running Make You Lose Muscle?
  • Situations Where Running Burns Muscle Mass
  • How to Run Without Losing Muscle Mass

Let’s get started!

A person running down the road.

Does Running Make You Lose Muscle?

Many people ask, “Does running make you lose muscle?” or “How much should I run to not lose muscle?” The answer isn’t a simple yes or no or specific amount of time, because whether or not running burns muscle largely depends on your overall energy balance.

It takes energy to run, so running burns calories. According to the Third Law of Thermodynamics, energy can’t be created or destroyed; it can only be transformed from one form to another.

Therefore, the energy to run, or the calories that get burned, have to come from somewhere. 

Depending on the intensity of your run, which can be thought of as the percentage of your VO2 max you’re working at, your body will burn stored carbohydrates (glycogen) and fat (stored triglycerides in fat cells) to create most of the energy your muscles need for your workout.

At lower intensities, a higher percentage of these calories come from stored fat. As the intensity increases, the substrate ratio shifts, and most of the energy comes from stored glycogen.

A person with sunglasses running down a road.

Protein contributes up to about 10% of the energy needed when running at moderate to high intensities. The body only stores protein as muscle tissue, which means that to some degree, running does burn muscle. However, under most circumstances, the amount of protein, or muscle tissue, burned on a run is minimal.

This means that if you’re in a well-fed state and running less than 90 minutes or so, running doesn’t burn a significant amount of muscle protein.

However, the body can only store a maximum of about 2000 calories in glycogen stores. When glycogen is depleted, your body has to be metabolically flexible and burn a different fuel to create more ATP (cellular energy) for your working muscles.

If you’ve ever felt a sudden “bonking” or “hitting the wall” sensation when on a long run or during a marathon, you’ve experienced the dreaded glycogen depletion state.

The muscles can more rapidly generate energy by burning stored carbohydrates than by burning fat, which is why the muscles’ preferred fuel source for high-intensity exercise is carbohydrates: they can crank out more energy faster by burning carbs, helping meet the high demands of your intense workout.

You are forced to slow your pace when the muscles have to shift back to burning fat. This is met with a concurrent increase in the reliance on burning muscle protein for fuel as well.

Therefore, when you’re in a glycogen-depleted state, running burns more muscle mass.

A runner seated, holding her head.

Situations Where Running Burns Muscle Mass

As mentioned, running burns muscle mass predominately when you are in a glycogen-depleted state. This can occur primarily in any of the following four situations:

Doing Long Runs and Workouts

When you do a long run, you’ll deplete your muscle glycogen after 1.5-2 hours or so, depending on the intensity of the run, your body size, nutritional status, and fueling strategy. You can also deplete your glycogen by stacking your run and strength training workouts back to back without eating in between.

Running In a Fasted State

Running first thing in the morning on an empty stomach starts you out with somewhat depleted glycogen stores, because your body burns through liver glycogen during the overnight fast while you sleep.

A tired runner with her eyes closed, tired.

Running On a Low-Carbohydrate Diet

If you routinely limit your carbohydrate intake with a low-carb diet, such as the paleo diet or keto diet, your glycogen stores can deplete prematurely when you run.

Running In An Overall Negative Energy Balance State

Whether you’re extreme dieting or maintaining a significant caloric deficit every day to lose weight, your body is in a catabolic state and will likely burn more muscle when you run because you’re not taking in enough calories.

Muscle protein can end up supplying 15% or more of the energy during high-intensity runs, but in any of these cases of glycogen depletion, this relative percentage can increase significantly. In these cases, running is indeed burning muscle tissue.

So, let’s try and avoid these situations and get into our ways of how to run without losing muscle mass.

A way of how to run without losing muscle mass, lift weights such as this person doing a deadlift.

How to Run Without Losing Muscle Mass

It should be possible to preserve your muscle mass while training for a marathon or other running event, even if you have a fast metabolism and do not want to lose any weight. Similarly, if you’re wondering how to run without losing muscle mass while still losing body fat, follow the principles below:

#1: Spend Time Lifting Weights

Probably the most effective way to preserve your muscle mass as a runner is to engage in at least 2-3 total-body strength training workouts per week, or 4-5 days of body part split routines.

The goal of these workouts should be to build muscular strength and size, rather than muscular endurance. From a practical standpoint, this means lift the heaviest weights you can safely handle with proper form for 4-10 reps per set rather than lighter weights for 12-15 reps or more.

Higher loads trigger your hormones and muscle fibers to get bigger and stronger—an anabolic effect—which can help counter the tissue breakdown—catabolic effect—of long distance running.

Compound, dynamic, multi-joint strengthening exercises like squats, lunges, deadlifts, step-ups, pull-ups, and push-ups are some of the best exercises for building muscle mass.

A group of protein-filled foods including eggs, cheese, milk, seeds, meat and poultry.

#2: Eat Enough Protein

Muscle protein synthesis, or repairing and building new muscle tissue, requires adequate protein intake

Protein is one of the three primary macronutrients. Along with carbohydrates and fat, protein provides energy (4 kcals per gram), but it also offers unique recovery and muscle-synthesis benefits. 

The protein we eat is broken down to amino acids, which are then assembled to make new proteins used to repair and rebuild muscles, tissues, cells, enzymes, and nucleic acids (DNA and RNA).

Protein also aids muscle recovery after running or strength training, helping heal any microscopic damage and building new muscle fibers to adapt to your training loads.

The American College of Sports Medicine recommends that athletes consume at least 1.2–2.0 grams of protein per kilogram of body weight per day. For example, a runner weighing 154 pounds (70 kg) should consume at least 84-140 grams of protein daily to meet their physiological needs.

While these recommendations are adequate for most runners, one way of how to run without losing muscle mass is to increase your protein intake to at least 1-2 grams per pound of body weight, particularly if you are in a negative energy balance (losing weight) or wanting to build muscle.

A person drinking a protein shake.

#3: Eat a Protein-Rich Meal or Snack Every 2-4 hours

It’s also important to space out your protein throughout the day, as the muscles use protein more effectively when it is delivered in moderate doses every few hours rather than large doses less frequently. Therefore, it’s not just about how much protein you eat—how often you eat protein is important as well.

Studies have demonstrated that ingesting 20 grams of protein immediately after exercise and then every three hours for the next 12 hours increases the rate of muscle protein synthesis more than having more protein less frequently (for example, 40 grams every six hours).

#4: Eat Protein After You Work Out

In addition to getting enough protein and eating protein regularly throughout the day, be sure that your post-run and post-workout fuel contains protein. Protein is vital for your post-workout recovery. 

A review of 11 studies found that cyclists who ingested protein along with carbohydrates after a workout saw improved performance (defined as both time to exhaustion and time trial performance) in the subsequent endurance ride by an average of 9% over cyclists who consumed just carbohydrates.

A person holding a kettlebell.

#5: Forget Intermittent Fasting

Because muscle protein synthesis is best supported when you eat at least 20 grams of protein every 3 hours (as opposed to 40 grams every six hours), one way to run without losing muscle is to eat small, frequent meals throughout the day.

#6: Space Out Your Workouts

For time efficiency, a lot of runners like to complete their cardio and weights in one session back to back. However, if you really want to build muscle and know how to run without losing muscle mass, it is best to split up your work out by at least several hours if not perform them on alternate days.

Strength training burns muscle glycogen, as does all but the lowest intensity runs (Zone 1 or Zone 2 training), so if you lift weights and then run or run and then lift weights without fueling in between your workouts, you are more likely to hit the glycogen depletion state and burn muscle tissue during your second workout.

A bowl of oatmeal with blueberries, nuts and honey.

#7: Don’t Run On An Empty Stomach

When you run or do cardio in a fasted state, there is little muscle glycogen on board to be burned for fuel. As such, there’s a greater chance that you will break down muscle tissue for energy.

If you are going to run first thing in the morning before breakfast, have a carbohydrate-rich snack, such as oatmeal, a banana or dried fruit, toast with butter and honey, or an energy bar, before heading out for your workout.

This will help top off your muscle glycogen stores and blood sugar levels to help ensure that muscle protein will only be used minimally to fuel your run.

#8: Fuel With Carbohydrates During Long Runs

Ingesting carbohydrates during long runs and races can help augment your glucose availability, providing a safeguard against burning too much protein for energy.

According to the American College of Sports Medicine (ACSM), ingesting 30–60 grams of carbohydrates per hour during endurance exercise is ideal.

This equates to 120-240 calories of carbohydrates per hour. These carbohydrates can come from sports beverages, energy gels or chews, or foods such as dried fruit, pretzels, bananas, or honey packets.

A person eating an energy gel on a cliff.

#9: Add HIIT

Long distance runs can catabolize, or break down, muscle tissue, but interval training may have the opposite effect.

One study found that a ten-week HIIT program increased muscle mass in the quads. Hill sprints, track workouts, and fartleks can be great options of how to run without losing muscle mass.

#10: Eat a Small Surplus of Calories

Most experts agree that to actually build muscle mass, you need a slight surplus of calories, so one very effective way to support running without losing muscle mass is to eat about 10 to 15% more calories per day than your body needs to maintain your weight.

In other words, if you burn 2000 calories a day, eating 2,200 calories or so can help maintain or build muscle mass when you strength train and run.

Follow these 10 tips on how to run without losing muscle mass and don’t let your fears of limiting your “gains” keep you from enjoying the miles.

To help you maintain a balanced, runner-friendly diet, check out our best diets for runners here.

A variety of healthy foods including berries, avocados, veggies and fruits.
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, and contributes to several fitness, health, and running websites and publications. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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