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What Every Weightlifter Should Know About Glycogen


If you want to know what glycogen is and how it affects your ability to build muscle and gain strength, then you want to read this article.

Key Takeaways

  1. Muscle glycogen is a form of carbohydrate that’s stored in your muscles and liver.
  2. Glycogen is the primary source of fuel during exercise, and low glycogen levels decreases your ability to gain strength and muscle.
  3. The best way to maintain high levels of muscle glycogen is to eat a high-carb diet, with around 1 to 3 grams of carbs per pound of body weight.

After decades of research, you can bet on a few “nutritional truths” when it comes to losing fat and building muscle:

Ask people “in the know,” about those ideas, and they’ll all more or less agree.

Ask them about how many carbs you should eat, though, and you’ll get a more polarized response.

Many will tell you that you need to eat plenty of carbs to build muscle and strength. Poke your head around some corners of the Internet, and it’s easy to think that you should be subsisting almost entirely on bread, pasta, and cereal if you want to get bigger, leaner, and stronger.

If you’re more interested in sports than throwing around weights, then you’ve also likely heard that most of your calories should come from carbs.

Why, though?

Well, their argument brings us to the topic at hand–muscle glycogen.

Higher carb diets increase your muscle glycogen levels, which improves your performance in every sport, they say.

Not everyone agrees, though.

Others say that high glycogen levels have no effect on muscle growth or strength gains, and can actually get in the way of fat loss.

When it comes to other sports, another group says that you can train your body to burn fat instead of carbs, so you don’t have to rely on muscle glycogen.

Still others say that glycogen is important, but you don’t need to eat carbs to keep your glycogen levels high.

So, who are you supposed to believe?

Well, here’s the truth:

If you want to build muscle and strength as quickly and efficiently as possible, with minimal fat gain, and/or you want to do well in sports, then you want to keep your glycogen levels higher rather than lower. The only way to do that, is to eat a high-carb diet.

In this article, you’re going to learn what muscle glycogen is, how it affects your strength, endurance, and body composition, how to tell if you have low muscle glycogen levels, how to boost your muscle glycogen levels, and more.

Let’s get started.

What Is Glycogen?

Glycogen is a molecule the body creates to store extra glucose, a kind of carbohydrate.

After a meal, your blood glucose (sugar) levels rise, especially if you ate a meal with some carbs in it. You need a certain amount of blood glucose to function, but you also don’t want high blood sugar levels for too long.

That’s why your body generally does one of two things when glucose levels rise:

  1. Your cells immediately use the glucose for fuel instead of fat.
  2. Your muscles and liver store extra glucose in the form of glycogen.

(If your glycogen levels are already maxed out, then your body starts converting carbs directly into fat via a process called de novo lipogenesis, but this is a very inefficient process in humans and rarely occurs).

Glycogen is made of thousands of glucose molecules that are linked together to form chains.

Here’s what it looks like:


Glycogen is primarily stored in your skeletal muscles and your liver, which you can think of as your glycogen fuel tanks.

Most people can store around 100 grams of glycogen in their livers, and around 500 grams of glycogen in their muscles, although people with more muscle mass and training experience can store considerably more than that.

All in all, most people will have around 600 grams of whole-body glycogen stores.

Your body uses the glycogen stored in your liver as an immediate source of energy to fuel your brain and perform other bodily functions throughout the day.

Your muscle glycogen, though, is generally depleted during exercise (or low-carb dieting).

Now, you may have heard people say that you don’t need to eat carbs to maintain high glycogen levels.

That’s simply untrue.

Your body can make glucose out of amino acids, but here’s the thing–that process only kicks into high gear when your body’s glycogen stores are running low.

It’s a backup plan that your body uses to keep your blood sugar in the healthy range, and it doesn’t produce enough glucose to restock your glycogen levels. In other words, it’s like running out of gas and switching to your reserve tank.

The only way to produce a significant amount of glycogen is to eat carbs.

Use this workout and flexible dieting program to lose up to 10 pounds of fat and build muscle in just 30 days…without starving yourself or living in the gym.

How Glycogen Affects Exercise

The most basic unit of cellular energy is a molecule called adenosine triphosphate (ATP).

For a cell to use ATP, though, it must first break it down into several smaller molecules. This process produces byproducts that are then “recycled” back into ATP to be used again.

The more ATP your cells can store and the faster they can regenerate it after use, the more work they can do. This is true of every bodily system, including your muscle cells.

When you exercise, your body requires far more ATP than usual.

For example, during a hard set of sprints your body may generate ATP 1,000 times faster than you do at rest.

So, where does all of that energy come from?

Well, several places.

Your body uses three different processes, known as “energy systems” to make sure that your muscles always have a steady supply of ATP no matter how hard you train.

These systems use other sources of energy, including body fat (triglycerides), glycogen, and another molecule called phosphocreatine, to regenerate ATP.

The three energy systems are:

  1. The phosphocreatine system.
  2. The anaerobic system.
  3. The aerobic system.

To understand how glycogen fits into all of this, we need to take a closer look at how each of these systems work.

1. The phosphocreatine system.

Phosphocreatine, also known as creatine-phosphate, is another source of energy stored in muscles.

The amount of phosphocreatine stored in muscles is small, Muscle can’t store very much phosphocreatine, though, and this system can’t produce as much total energy as the other two. The advantage of phosphocreatine, though, is that it can be used to regenerate ATP much faster than any other energy source.

That is, the phosphocreatine system can’t produce much energy, but it can produce it almost immediately.

That’s why the body relies on the phosphocreatine system for brief, intense efforts that last around 10 seconds or less, like a one-rep max bench press.

There’s a downside to this system, though.

It takes a long time for phosphocreatine to reach normal levels after a hard effort, sometimes as long as 5 minutes. (This is why taking creatine improves your performance–it improves the efficiency of your phosphocreatine system).

After about 10 seconds, though, your body needs to get more energy from other sources.

2. The anaerobic system.

After around 20 seconds of effort, the anaerobic energy system starts producing the majority of energy for ATP regeneration.

This is called the “anaerobic system,” because it regenerates ATP without the presence of oxygen. (“An-” meaning “without,” and “aerobic” meaning “associated with oxygen.”) This allows it to produce energy faster, but not as efficiently as the aerobic system.

This is also referred to as the “glycolytic system,” because it gets the majority of its energy from glycogen and glucose.

It’s primarily used for efforts that last around 20 seconds to 2 minutes, or anything that makes your muscles “burn.” This burning sensation is thanks to metabolic byproducts that build up in your muscles as a result of anaerobic energy production.

Most of your sets in the gym will be powered by your anaerobic system.

3. The aerobic system.

The aerobic system, also called the “oxidative” or “respiratory” metabolism, takes over after about 60 to 90 seconds of effort.

This system can’t produce energy as quickly as the first two, but it can produce it for a much greater length of time and does so much more efficiently.

It also burns through a lot of muscle glycogen when you’re training hard.

All three of these energy systems are working all of the time, but the contribution of each varies depending on how hard you’re working.

The harder you exercise, the faster your body needs to regenerate ATP, and the more it relies on the first two systems–the phosphocreatine and anaerobic energy systems. Your aerobic system also kicks into gear during your workouts to help regenerate ATP, especially when you’re recovering between sets.

And do you know what your body’s favorite source of energy is for regenerating ATP?

Glucose, which it primarily gets from glycogen.

We don’t need to get into the details, but all three of these systems rely on carbohydrate either directly or indirectly to one degree or another.

When your glycogen levels get too low, your body isn’t able to regenerate ATP as quickly, and you have to reduce the intensity of your workouts.

If you keep your glycogen levels high, though, then you can train harder and for longer.

Let’s take a look at how this affects both strength and endurance training.

Glycogen and Strength

glycogen and strength training

If you’re doing most of your sets in the 4 to 6 rep range, then your sets will typically last around 15 to 20 seconds total.

So, if muscle glycogen is primarily used for longer efforts (over 20 seconds or so), then why should it make any difference in your ability to throw around heavy weights?

Well, there are a few reasons.

First, even though you primarily rely on the phosphocreatine system during short efforts, you still use a fair amount of glycogen, too.

For example, during a 10 second sprint, your muscles get about half their energy from the phosphocreatine system and about half from your anaerobic system. Over the course of 6 to 9 sets, that can deplete muscle glycogen levels by around 40%.

This is why doing something like a one-rep max can still feel harder when you reduce your carbohydrate intake.

Second, between sets, your aerobic system relies heavily on carbohydrate to regenerate ATP. If you don’t have enough glycogen in your muscles to adequately recover between sets, then your performance is going to feel worse and worse the longer your workout drags on.

Now, to be fair, there aren’t that many studies on how carbohydrate intake affects strength gains.

We do know, though, that high-intensity training heavily relies on carbohydrate.

When people do other kinds of high-intensity exercise, like sprinting, running, or jumping, they almost always perform better when they eat more carbs.

If we look at high-level strength athletes, we see that they also eat a ton of carbs.

Specifically, strength athletes eat around 4 to 6 grams of carbohydrate per kilogram of body weight. For a 200 pound man, that’s 350 to 550 grams of carbohydrate per day.

The bottom line is that if you want to get as strong as possible, you want to follow a high-carb diet.

Glycogen and Endurance

Your body reaches its peak glycogen usage when you reach around 50 to 85% of your maximum intensity, which includes just about every endurance sport.

This is why you see runners pounding bananas, bagels, and bars before runs, and why there’s a massive industry for sports drinks, gels, chews, and anything else that contains carbs.

As you get closer to the top end of that intensity range, your body uses exponentially more carbohydrate. That is, if you train at 60% of your maximum intensity, you’ll use more than twice as much glycogen as you do when training at 30%.

When you run out of glycogen, you can’t maintain the same pace. It’s physically impossible.

There’s a reason endurance athletes call running out of glycogen “hitting the wall” or “bonking.”

You can prevent this from happening by eating carbs during long workouts and maximizing your glycogen stores by eating a high-carb diet the rest of the time.

What if there were a way to avoid this altogether, though?

Glycogen isn’t the only source of fuel your body uses during endurance exercise. It also uses a fair amount of body fat.

As you get in better shape, your body becomes more efficient at tapping into its fat stores, so you use less glycogen at the same pace.

This fact has led some people to believe that you can become “fat adapted.” Follow a low-carb diet, and you’ll teach your body to burn fat instead of carbs, so you don’t need to rely on glycogen, they say.

As long as you go slowly, this strategy can more or less work. Putter along at a slow pace, and you don’t need many carbs (although you probably won’t feel that great).

The problem is that if you want to do well at running, cycling, rowing, or any other endurance sport, then you want to go as fast as you can. You don’t want to move at the same pace you have in the past, you want to incrementally go faster and faster, which is going to require more and more glycogen.

And that’s where the idea of “fat adaptation” falls apart.

When it comes to hard training and racing, people who eat more carbs beat those who eat fewer carbs every time.

This is also why every single credible study on nutrition for endurance athletes recommends you eat a high-carb diet if you want to perform at your best.

There’s just no getting around it–every endurance sport requires you to train and race at a pace that uses a massive amount of glycogen. The only way you’ll be able to maintain that pace is if your muscles have a lot of stored glycogen.

How Glycogen Affects Body Composition

glycogen carbohydrate

When it comes to losing fat and building muscle, carbs (and by extension, glycogen), get a bad rap.

Eat too many carbs, and it will be impossible for you to improve your body composition, or so many claim.

Many also say that carbs don’t help you build muscle, so it would seem they’re all con and no pro.

The truth, though, is quite different.

You can lose fat and build muscle following a low-carb diet, but you’ll make faster progress if you follow a high-carb diet instead.

Glycogen and Muscle Gain

If you want to build muscle as quickly and efficiently as possible, then you want high muscle glycogen levels for two reasons.

  1. Higher glycogen levels let you train harder.

The primary driver of muscle growth is progressive tension overload, which involves exposing your muscles to greater and greater levels of tension over time.

The best way to do that, is to get as strong as possible on the big, compound lifts.

If you keep your glycogen levels high, then you’re going to gain strength faster, which means you’re going to gain muscle faster, too.

So, indirectly at least, having higher levels of muscle glycogen should help you build muscle faster.

  1. Higher glycogen levels improve recovery.

When it comes to building muscle, how well you can recover from your training is just as important as the workouts themselves.

Low muscle glycogen levels are associated with overtraining, and low-carb diets, which deplete muscle glycogen, also increase cortisol and reduce testosterone levels in athletes.

Low-carb diets also reduce insulin levels. In addition to helping store nutrients, insulin also has powerful anti-catabolic properties. This means that insulin decreases the rate at which muscle proteins are broken down, which creates a more anabolic environment conducive to muscle growth.

Maintaining high muscle glycogen levels also improves the post-workout genetic signaling related to muscle growth and repair.

It would be a stretch to say that boosting your muscle glycogen levels directly causes muscle growth, but it probably helps by letting you train harder and bounce back faster from your workouts.

Glycogen and Fat Loss

There are all kinds of theories out there on why low-carb diets might help you lose fat faster.

“It keeps your insulin levels lower.”

“It reduces your hunger and cravings.”

“It balances your hormones.”

And every one of these ideas has been categorically and definitively debunked. As long as you maintain an energy deficit, you’ll lose weight regardless of whether you get most of your calories from carbs, protein, or fat.

Chances are, you’re on board with that idea, too.

You may have heard, though, that you need to deplete your glycogen levels to maximize fat loss. This is particularly true once you reach about 15% body fat for men and 25% for women.

Once you reach this point, they say, you have to exhaust the glucose stored in your muscles to slim down to the chiseled physique you want.

Not only is that not true, doing so can slow your progress.

To improve your body composition, you want to lose fat while maintaining or building muscle mass.

If you cut your carb intake and your glycogen levels, you’ll perform poorly in your workouts, recover slower, and likely lose some strength and muscle mass.

And all three of those things are going to make it harder to get the body you want.

Maintaining higher muscle glycogen levels won’t make you lose more fat, but it will help you avoid losing muscle.

What Are the Signs of Low Glycogen Levels?

low glycogen

There are a few telltale signs that your muscles are low on glycogen:

  • Your workouts feel awful.

If you’re getting enough sleep and are following a sensible workout routine, and suddenly every weight feels three times heavier than it should, you’re probably glycogen depleted.

This is particularly true if you feel worse the longer you’re in the gym. Remember, glycogen is your main source of fuel during weightlifting, so the longer you train without adequate fuel, the harder it’s going to feel.

  • You lose several pounds overnight.

Every gram of muscle glycogen is stored with 3 to 4 grams of water.

A pound is 454 grams, so if you eat 110 grams of carbs (three cups of cooked pasta), you can gain about a pound of total body weight.

On the flipside, if you burn through the majority of your glycogen stores, then you can also lose several pounds in a matter of hours.

While that’s gratifying in the short-term, it can also be a sign that you need to replenish your muscle glycogen.

There are other things that can cause you to lose or gain water weight, but changes in glycogen levels tends to be the big one.

How to Increase Your Glycogen Levels

One large high-carb meal isn’t enough to keep your glycogen levels elevated.

Glycogen is always being broken down and regenerated, which is why you have to maintain a relatively high daily carbohydrate intake.

How much, exactly?

If you’re trying to get stronger and build muscle, then you want to eat around 1 to 3 grams of carbs per pound of body weight.

If you want to lose fat, then your carb intake will largely be dictated by how many calories you have left after setting your protein and fat targets. For most people, this will work out to somewhere around 1 to 1.5 grams of carbs per pound of body weight.

If you’re an endurance athlete, then you’re going to burn through far more muscle glycogen than the average gym goer. You may need as much as 4 to 5 grams of carbs per pound of body weight to keep your glycogen levels topped off.

Here’s an example of how astronomically high your carb needs are during endurance training. The latest research suggests that if you’re training for more than two or three hours at a time, you should try to consume around 90 grams of carbs per hour.  That’s about 1 full-size bagel every 30 minutes. 

Chances are good that you aren’t in that boat, and you’ll be able to keep your glycogen levels high with a lower daily carb intake.

The bottom line, though, is that you generally want to eat as many carbs as you can after ensuring you’re getting enough protein and fat every day.

The one exception to that rule is if you have a lot of weight to lose, in which case you’re better off sticking with a low-ish carb diet until you reach a lower body fat percentage.

If you want to learn more about how many carbs you should eat, check out this article:

How to Know Exactly How Many Carbs You Should Eat

The Bottom Line on Glycogen

glycogen function

If you want to…

  • get stronger,
  • build muscle faster,
  • and improve your body composition…

…then you want to keep your muscle glycogen levels relatively high.

Not only will that not get in the way of fat loss, it’ll make your next cut more productive.

To maximize your glycogen levels, you need to eat a high-carb diet.

Do that consistently, and you’ll be happy with the results.

If you liked this article, please share it on Facebook, Twitter, or wherever you like to hang out online! 🙂

What’s your take on glycogen? Have anything else to share? Let me know in the comments below!

armilegge Armistead Legge is the Editor-in-Chief for Muscle for Life and Legion Athletics. He has completed over 100 triathlons and cross-country, cycling, and adventure races, and has researched and written for over a dozen organizations, including the National Institutes of Health. When he isn't helping people get into the best shape of their lives, he's lifting weights, riding his bike, hiking, camping, reading, and making delicious food.


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