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Home » OSL Blog » What is Glycogen?

What is Glycogen?

May 22, 2019

  1. Do you avoid eating carbohydrates because you believe that you will get fat from eating too many carbs?
  2. Do you notice a difference in your energy levels during your workouts when you don’t eat enough carbohydrates throughout the day?
  3. What are your favorite types of carbs to eat for energy and efficiency during your workouts?

As a serious bodybuilder, it’s not enough to just lift weights to build muscle to create the physique you aim for.

You also have to understand:

  • Nutrition
  • The proper ways to fuel your body based on your goals
  • Foods to avoid and foods to eat
  • How the body stores and uses energy
  • The right ways to supplement – what to use and what to avoid

Failing to fuel your body properly can not only stall your progress, but it can also lead to muscle fatigue, weakness, and potential injury.

Both nutrition & exercise are important for bodybuilding.

If you are a bodybuilder looking for maximum muscle growth and ways to recover faster from intense workouts, make sure you read this article. You will gain valuable information on:

  • How glycogen is used before, during, and after workouts
  • The different systems your body uses to create energy and the role of glycogen to keep them running smoothly and function properly
  • How to fuel your body correctly to get the results you’re looking for
  • The role carbs play in recovering muscles

What is Glycogen?

First, let’s take a look at:

  • What glycogen is
  • What role it plays in the body
  • Why glycogen is so important to your daily workout
  • Ways to make sure your glycogen supply is high so that your body reaps the benefits

Glycogen is a sucrose polysaccharide (carbohydrate consisting of bonded sugar molecules) that is stored primarily in the liver and secondarily in muscle cells. A very small amount of glycogen is also found in the brain, liver, and kidneys as well.

Glycogen is made up of mostly water. It’s stored as granules in the cytosol, or liquid, inside your cells along with other vitamins and minerals. It remains in your cells until the body signals that it needs more glucose, and then it starts transforming into fuel for your body in the form of energy.

It is a form of energy storage for:

  • Humans
  • Animals
  • Fungi
  • Plants
  • Bacteria

Glycogen Breakdown

When you eat carbohydrates, they are broken down into glucose in the body. Glucose fuels our cells and is the main source of energy created within the body.

When glucose first enters the body, any amount needed to maintain energy levels is immediately used. The remaining glucose is stored in the liver and muscles as glycogen until it is needed. Once the signal is sent, the process to convert glycogen back to glucose to be used as energy begins.

Glycogen breakdown is a multi-step, complex process that starts in either the liver or the skeletal muscle cells. If energy is needed in any other part of the body other than the muscles, the glycogen is sent from the liver cells.

Glycogen structure

The long-branch structure allows for just the right amount of glycogen to break off, leaving the remaining molecules in place to be used the next time around. This also allows for new glycogen to attach to the structure, waiting in the wings to be called up to bat once needed.

Glycogen aids in creating steady energy levels, reducing the risk of spiking blood sugar with high glucose levels.

Glycogen’s Role in the Liver

Glycogen levels make up as much as 10% of the liver mass in a typical human. When insulin levels are low, a catabolic hormone (adrenaline and cortisol are also catabolic hormones) called glucagon is released by the pancreas. This signals the breakdown of glycogen in the liver.

A process called glycogenolysis breaks down the glycogen into glucose-1-phosphate. The newly formed glucose-1-phosphate enzyme is then able to be released into the bloodstream so that it can travel wherever it needs to in the body to provide energy.

The liver itself does not use the glucose it stores, rather it helps to breakdown the glycogen within its cells to be available for the rest of the body to use.

Glycogen’s Role in the Muscle

Glycogen only makes up about one percent of your muscle mass. Since there is more muscle mass to liver mass in the body, overall there is more glycogen stored in the muscle cells than liver cells at any given time.

When your body is completing a strenuous activity, like weight lifting, the body signals the breakdown of glycogen. This happens in the muscles specifically being used, to produce energy.

Strenuous exercise like weightlifting signals the breakdown of glycogen.

What does this mean?

  • If you’re doing squats, your quadriceps, calves, glutes, and hamstrings will all start to break down the glycogen within those muscles
  • If you’re doing push-ups, then your body signals the shoulders, arm, and chest muscles to start breaking down glycogen when reserves get low

In the muscle fibers, glycogen degrades and synthesizes further from the glucose-1-phosphate form to become the glucose-6-phosphatase enzyme. This enzyme form is then able to be absorbed by the muscle tissue and can be used as energy to supply the muscle.

When your muscles contract, it sends a signal to the brain that more glucose is needed, and the process starts. The next time you feel that boost of energy in your muscles that help you maintain your high-intensity workout, you can thank your glycogen stores for taking action.

The Body’s Energy Systems

There are three main energy systems that the body uses to create adenosine triphosphate (ATP). Sometimes called the “molecular unit of currency,” ATP stores and transports energy within the body’s cells.

Without these systems in place, your body would not be able to replenish the energy you are depleting when exercising. Each system plays a different role in your training program.

The Phosphocreatine System

The phosphocreatine system, sometimes called the phosphagen system, is the first system your body uses when working out. As your ATP levels are reduced, this system starts working to create more energy.

This happens incredibly fast. Your muscle contracts and uses almost all of its ATP energy, so the body signals for more creatine to be sent to that muscle. Most of the creatine is absorbed into the muscle which creates phosphocreatine.

Your body drains the phosphocreatine after about 10 seconds of muscle contractions and it takes up to 10 minutes for more creatine to be sent to the muscle.

Your phosphocreatine is depleted after:

  • Throwing a ball one time
  • Lifting a weight one repetition
  • Sprinting
weighlifter one rep
Weightlifting depletes the phosphocreatine system.

While it’s waiting for that system to gear back up, the anaerobic system jumps in to help out.

The Anaerobic System

Also called anaerobic glycolysis, this system does not use oxygen but instead uses glucose energy to create more ATP. The glucose is broken down into pyruvate within the cells.

With rapid creation of ATP, the anaerobic system is able to energize your muscles for up to three minutes. The next time you feel your muscle start to burn, you can imagine your anaerobic system hard at work.

The Aerobic System

Also called the aerobic glycolysis, this is the long range system that forms ATP for sustained energy production. It does require oxygen to burn carbohydrates and fat into energy.

Once the phosphagen and anaerobic systems have been properly fatigued, the aerobic system kicks it. This usually happens when you are in between sets or during moderately intense workouts.

Depending on the duration and difficulty of your workout, your body will use all three systems. Each one plays a role in your energy usage, and without glycogen, your body would not be able to work through these systems to create energy correctly.

Glycogen Storage Disease

When your body cannot store and use glycogen properly, you may have a health issue called glycogen storage disease (GSD). The body is typically missing a required enzyme for metabolization, and can cause glycogen to either not form properly, or build up in the liver.

Glycogen storage disease is typically diagnosed in children and there is no way to prevent GSD from being passed down to the child. Glycogen storage disease is a hereditary disease and is passed down by both parents.

Some people have no symptoms or aren’t diagnosed until they are adults. To find out if you are a carrier of the GSD gene, you would have to undergo genetic testing to determine if you are a carrier. This does not mean that you will actually have GSD yourself, but you could potentially pass it along to your child if your partner also carries the gene.

Types of GSD

There are four different type of glycogen storage disease:

  • Type I – also called von Gierske disease. Symptoms start in babies as young as a month old, and present as low blood sugar or a distended stomach from an enlarged liver. This is the most common type and is caused by glycogen buildup in the liver due to lack of enzyme to turn glycogen into glucose to be stored in the liver.
  • Type II – also called Pompe disease or acid maltase deficiency disease. This type can take two forms. One presents within the heart of a baby younger than 12 months old, and the other does not and can affect children that young or older. The gene needed to signal acid maltese use to help break down glycogen is missing. It creates a buildup of glycogen in cells. The first form is more serious and can be fatal to babies, the second form is milder and could cause breathing problems.
  • Type III – also called Cori disease or Forbes disease. The debranching enzyme in charge of breaking down glycogen is missing. This causes glycogen to build up in the liver and muscle tissues. Swollen belly, weak muscles, and delayed growth are the most common symptoms.
  • Type IV – also called Anderson disease. While not definitive, experts suspect that abnormal glycogen formed by this type of glycogen storage disease incorrectly triggers the immune system. This can cause cirrhosis of the liver, as well as scarring on other organs including muscles and the heart.


Some of the most common symptoms to look for if you suspect you or someone you love, especially a child, has GSD:

  • Slow growth
  • Heat intolerance
  • Skin easily bruises
  • Low muscle tone
  • Pain and/or cramping in muscle during exercise
  • Low blood sugar
  • Enlarged liver
  • Swollen abdomen
  • High blood cholesterol
  • High acid levels in the blood

Each type of GSD can create specific symptoms, depending on the enzyme that the body is lacking.

Exercise and Glycogen Depletion

People who train regularly or participate in endurance sports use more of their glycogen levels than people who are sedentary or don’t work out regularly.

This can cause glycogen depletion. If you’ve ever experienced a drop in blood glucose levels, it isn’t something you want to ever happen during a workout.

Hypoglycemia occurs when blood sugar drops and can cause:

  • Sudden, extreme fatigue
  • Dizziness
  • Hallucinations
  • The feeling of complete loss of power

If you have ever seen someone suddenly collapse, especially marathon runners or people competing in extreme competitions, you’ve witnessed hypoglycemia. This is also called “bonking” or “hitting the wall” in the fitness world.

Endurance runners
Endurance athletes encounter cases of hypoglycemia.

Without glycogen to convert into energy, the body will search for other ways to create glucose. One way it will do this is to produce cortisol by breaking down muscle tissue. By doing so, it converts muscle proteins into glucose to provide energy. This can contribute to muscle atrophy, decreasing overall muscle mass.

This is not something that any serious powerlifter, weightlifter, or bodybuilder wants to happen to them.

One way you can avoid this from happening is to eat high carbohydrate foods prior to working out. The carbs will create larger stores of glycogen in both the liver and muscle cells, providing as much energy as needed to keep your workouts going.

Carbohydrates Role in Bodybuilding

Some bodybuilders believed back in the Golden Era that low-carb diets were king. They thought that carbs were the devil and a surefire way to invite fat to stay. These misconceptions are still prevalent in some minds to this day.

Golden Era legend Tom Platz knew even back then that a low carb, high-fat diet wasn’t always the right answer. When switching to high carbs for the 1980 Mr. Olympia contest, he reaped the benefits. He was in the best shape of his life, bigger and better than ever.

Tom Platz
In 1980 Mr. Olympia, Tom Platz was a life proof of the benefits of a high-carb diet.

Studies have shown that eating a high carbohydrate diet when training, especially for endurance training, is the best way to ensure that glycogen levels are able to be restored as fast as you are burning them.

Eating slow-digesting carbs before you work out is a great way to ensure that your energy levels remain high throughout your workout.

Foods High in Carbohydrates

Foods to Eat More Of

High carb foods

Examples of high carbohydrate foods to eat:

  • Quinoa – 21% carbs
  • Bananas – 23% carbs
  • Sweet potatoes – 19% carbs
  • Raw oats – 66% carbs
  • Beets – 8% carbs
  • Blueberries 14% carbs
  • Oranges – 12% carbs
  • Apples – 13 – 15% carbs depending on variety
  • Grapefruit – 9% carbs
  • Chickpeas/garbanzo beans – 27% carbs
  • Kidney beans – 23% carbs
  • Buckwheat – 71% carbs
  • Dates – 6% carbs
  • Mango – 9% carbs
  • Raisin – 38% carbs

Eating these whole foods before and after your workout provides your body with the needed essential nutrients to fuel your workouts.

When fueled properly, the glycogen stored in your liver will metabolize and feed your muscles.

Foods to Eat Less Of

Junk food

Some foods are high in carbohydrates but should still be avoided. They are typically devoid of any other nutritional value and are high in white sugar. They can cause unsafe spikes in glucose levels, causing you to burn out during your workout.

To avoid derailing your fitness goals, steer clear of these high carb foods:

  • Candy
  • Fried foods
  • Soda
  • White bread
  • Foods with high levels of high fructose corn syrup (HFCS)
  • Sugary cereals
  • Baked goods – cookies, cakes, pastries, muffins
  • Flavored and sweetened yogurts

How Many Carbs Should I Be Eating?

The amount of carbs you need depend on your weight, training level, and type of result you are looking for.


  • Bulking – aim for one to three grams of carbs per pound of body weight per day
  • Cutting – aim for one to one and a half grams of carbs per pound of body weight per day
  • Endurance training – depending on how much you train, you want to aim for anywhere from two to five grams of carbs per pound of body went per day

Here’s an example:

Jim has really been focusing on bulking to hit his goal for competition. He currently weighs in at 235 pounds. Since he is in the bulking phase right now, he should be eating between 235 and 705 grams of carbs per day.

Once he starts the cutting phase, he’ll want to reduce his daily carbohydrate intake to between 235 and 352.5 grams per day.

We suggest starting on the higher end when bulking, but reducing as needed if you experience stomach upset or pains while working out. Listen to your body and try different foods high in carbs to see what works best for you when you’re working out.

The Risk of Restricting

Some people think that restricting calories and certain foods are still the best way to reduce overall body fat. And for some, that can be true. But, when you are a bodybuilder and looking to gain muscle and reduce body fat, restricting is probably not the best way to go.

Carbohydrates are said to be “protein-sparing” because when there are enough carbs in the body, they can be utilized as energy. When carbs are low and the body is in need of energy, it can resort to actually breaking down protein in the muscles in order to obtain the energy it needs. This situation can be avoided as long as there are plenty of carbohydrates available as an energy source.

This study shows the results of properly fueling your body during and after a workout. Over an 11-week period, 14 bodybuilders were tested to determine how restricting affects hormone levels and body mass. Seven bodybuilders were in the control group and seven in the restricted group.

body comparison
Restricting calories affects hormone levels and body mass.

They found that the restricting group showed reduced fat mass, lean mass, and overall body mass. This is great, right? It did exactly what it was supposed to do – reduce body fat.

But they also reduced all three of their anabolic hormones – insulin, testosterone, and IGF-1 (growth hormone). Those hormones are crucial to bodybuilders, as all are needed to build muscle and provide stamina and energy, just like the catabolic hormones.

Glycogen Supplement

For some people, eating high carb foods can cause gastrointestinal issues, especially during training.

To combat this, some people choose to use supplements and drinks during and after working out.

If you choose to go this route, know that there are some options that are better for you than others. Gatorade your drink of choice? Consider reading this article to find out if there are better alternative sports drinks available.

That said, if you prefer to take supplements during and post workout, consider a supplement like Vintage Build™ as your post workout option. It contains branch-chain amino acids, creatine monohydrate and l-glutamine to help muscles build and repair.

Vintage Build
Vintage Build contains branch-chain amino acids, creatine monohydrate & l-glutamine.

Another option would be to consume a quick acting carbohydrate food source immediately following your workout. Choose a low-fiber, high glycemic carb like white rice to replenish the glycogen stores in your muscles as quickly as possible.

Do you or someone you know have GSD? How does this affect their fitness goals and general health? Did you enjoy learning about glycogen and its role in helping you gain muscle and fuel your workouts? Let us know in the comments.

Disclaimer: None of the individuals and/or companies mentioned necessarily endorse Old School Labs or COSIDLA Inc. products or the contents of this article. Any programs provided for illustration purposes only. Always consult with your personal trainer, nutritionist and physician before changing or starting any new exercise, nutrition, or supplementation program.
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