Get to Know Your Metabolism and Running

Here, Hnatiuk and Thomas G. Allison, Ph.D., M.P.H., director of the Mayo Clinic sports cardiology clinic in Rochester, Minnesota, explain all you need to know about these essential metabolic reactions that work simultaneously in your body, both during runs and at rest.

Anabolic vs. Catabolic—What You Need to Know

According to the National Library of Medicine, metabolism covers “the whole sum of reactions that occur throughout the body within each cell and that provide the body with energy.” Just as your heart beats all the time, your metabolism is also at work all the time.

However, just as your heart beats at different speeds during various activities, your metabolism works differently depending on what your body is doing. Specifically, within your overall metabolism are both the anabolic and catabolic processes.

Anabolic processes require energy while catabolic processes release energy. In a nutshell, anabolism uses energy to repair and rebuild body tissues, such as muscle after a workout, while catabolism occurs when your body breaks down food to get the energy from it, explains Hnatiuk.

As a runner, you know that when you recover from a race, you don’t just lie around, you also eat protein and carbs to rebuild and refuel. Therefore, both anabolic and catabolic processes are occurring within your body at the same time—catabolism is in action to turn those foods into energy while anabolism uses that energy to repair your body.

Therefore, when someone on social media sets up these two systems as working against each other, they may get some clicks, but they aren’t relying on facts, considering these systems work together.

Anabolism: The process of smaller molecules joining to form larger molecules, such as amino acids, cells, and nutrients. “For example, repairing muscle tissue after a strength training session is an anabolic process,” says Hnatiuk. Anabolism is also at work when the body repairs a cut or a child grows.

Catabolism: “Catabolism is all about breaking down, depleting, or damaging,” says Allison. During digestion, the catabolic process breaks down food into nutrients that your body uses for energy. When your body isn’t getting the nutrients it needs for daily living, catabolism is also the mechanism that breaks down muscle and fat for energy. In certain illnesses, “wasting disease” is the extreme result of being in a prolonged catabolic stage.

The Role Anabolic and Catabolic Metabolism Play in Running

Running, like any sustained physical activity, is catabolic. “While you are exercising, you’re depleting glycogen, you’re damaging muscles, you’re using up triglycerides,” explains Allison.

The most important thing for runners to keep in mind is that the more intensely you train, the more your body is engaged in catabolism. This isn’t a bad thing—you need this catabolic breakdown to occur in order to get fitter, faster, stronger, or generally healthier.

But you do need to balance catabolism with anabolic processes, like rest and sleep. During rest, muscle damage is undone and the rebuilding of muscle occurs. Without enough rest, the repeated stress of catabolic exercise can lead to excessive muscle soreness, fatigue, injury, or illness. In other words, overtraining. “A good guide is to only train as hard as you have time to recover,” says Hnatiuk.

Of course, just as you likely manipulate your training to reach certain goals, such as doing intervals to improve your pace and VO2 Max, you can also (sort of) manipulate these metabolic processes to help you both train and recover.

How Hormones Affect Anabolism and Catabolism

Even though you don’t want to set up anabolism and catabolism as enemies, you do need to understand how they work in relation to other bodily systems, and one of their most important interactions is with hormones. Having healthy levels of hormones will affect the abilities of these systems to help you run and recover as needed.

For example, exercise is a catabolic stress on the body, and all stress increases cortisol, the stress hormone. “The body can’t differentiate between different types of stress. It’s all just stress,” Hnatiuk says.

For this reason, Hnatiuk says savvy runners who understand anabolism/catabolism know not to push their running too hard, especially if there is other stress in their lives. “If you do [push it when you’re stressed], you’re going to see a lack of recovery and issues with being able to maintain whatever volume or intensity you’re trying to get to,” she adds.

Building muscle, an anabolic process, is linked to hormones produced by the thyroid, as well as testosterone and growth hormone. Low levels of these hormones combined with not eating enough can make a runner experience a higher rate of catabolic reactions (the breaking down of muscle tissue) compared to the anabolic reactions needed to build and maintain muscle. That means you’ll lose muscle mass and probably feel fatigued. This can also negatively affect your running speed, warns Allison.

On the other hand, if you overconsume calories and eat more than your body needs, you trigger your body to complete additional anabolic reactions, also known as the storage of muscle glycogen or body fat. This may sound familiar—it’s close to the concept of carbo loading. However, carbo loading isn’t about overconsuming calories—it’s more about getting most of your calories from carbs, while reducing fats and proteins so you maximize your glycogen stores a couple of days in advance of a longer race.

How to Support Both Anabolism and Catabolism

Despite what you might hear on social media, you can’t control anabolism or catabolism with individual food selections or supplements. Eating a lot of protein won’t automatically spur anabolic processes and therefore, build up muscle mass, for example (even though it can contribute to muscle building). What’s better: Eating adequate protein, engaging in muscle-building exercise (like weight training), and resting adequately.

“It’s less a matter of choosing the right foods [to control the metabolic process], but more about ensuring we have the right balance of total calories and macronutrients—fat, protein and carbohydrate—to support optimal metabolism in both directions, catabolic and anabolic,” says Hnatiuk.

Key Takeaways about Anabolism and Catabolism

“Rather than overthinking it or trying to micromanage our metabolism, our bodies do best when we focus on adequate nutrition for our running demands, and allowing for proper recovery—sleep and rest—between runs,” says Hnatiuk. This is the best way to work with anabolism and catabolism.

Both Allison and Hnatiuk advocate for a healthy diet with enough calories to maintain daily functioning and cover the physical activity you do through running and other workouts. Avoid fad diets and supplements that claim to hijack your catabolic and anabolic processes to improve your run.

“If you want to run faster, train harder,” says Allison, who has completed 26 marathons. “We can’t substitute dietary magic for time on the track, miles on the road, or hours in the weight room.”

Victoria Clayton is a freelance writer whose work has appeared in The Atlantic, The Washington Post, The Guardian, and many other publications. She loves to run and hike in the Santa Monica mountains near her Southern California home.