If you are into fitness or have been trying to become more healthy, you have probably heard the word “insulin” being thrown around. What is insulin and what role does it play in your body?

If you read some nutrition “gurus”, insulin gets a bad rap. Especially guys who argue that carbohydrates are evil and push low-carb diets, try to point the finger at insulin as one of the main causes of people getting fat. They argue that carbs are bad and insulin is bad by association.

However if you look at their arguments more closely, you can see that they make pretty sketchy connections and their conclusions are pretty much BS.

In order to be able to analyze all the different diets that people are hyping-up and make an informed choice on which is the best for you, you need to know what insulin is and how it works.

Let’s start by listing the main roles of insulin in the body:

1) push glucose into cells, in order for it to be used as energy

2) push other types of nutrients (for example proteins), in order for them to be used by the cells

3) store excess glucose for later use (either as glycogen or fat)

Remember these roles when reading the rest of the article, as this is crucial for understanding the importance of insulin in different bodily processes, and especially in what role it plays in getting bigger muscles and losing fat.

Insulin is one of the most important hormones for your metabolism. The different cells in your body need glucose for energy and insulin promotes the absorption of glucose by them (either for energy or for storage – glycogen, fat).

It is a peptide hormone, which means that it’s a functional protein. It is produced in the pancreas by beta cells and serves many functions in your body. You can think of it as the main regulator of your body.

Insulin is released into the bloodstream when glucose is present, whether due to food getting ingested or due to different stress hormones flooding the body.

What happens is that when you are eating, the food is broken down into its more basic constituent parts, and the pancreas starts releasing insulin into your bloodstream. The insulin then directs the transport of these nutrients either into the cells or for storage. Once the level of these nutrients in the blood drops, then the amount of insulin drops as well.

Let’s use an analogy in order to illustrate how insulin works. Imagine that insulin is a small spaceship that travels through your blood and muscle cells are big space factories. These space factories have docking stations (insulin receptors) that the insulin spaceship periodically visits and docks at them.

In the process, the insulin acts as a sort of key, unlocking the doors to the cells. Once these doors are unlocked, nutrients such as glucose or amino acids can enter the cells, bringing energy and also different building blocks for their internal processes.

When insulin is released, the body gets a signal to stop burning fat for energy and instead use the new food that just came in. At that point, insulin also begins the process of energy storage.

Once again imagine insulin as a small spaceship and fat cells as big storage depots. The insulin spaceship docks at the fat cell and tells it to start the process of storing all the excess energy for later use. This thereby increases body fat.


This role of insulin is why it is often depicted as one of the main reasons that people get fat. However this argument is based on a very simplistic reading of the situation.

Insulin is just a hormone which has a certain role to perform in the body. The way it performs it is based on external factors and especially on the choices that people make with their habits and their food.

High vs. Low-Glycemic foods (fast vs. slow absorbing)

The type of carbs you eat, has an effect on how your body controls insulin. If most of the carbs you ingest are high on the Glycemic Index, then you might have a problem. High-GI foods pass through the blood quickly, which can cause insulin spikes. This can result in reduced insulin sensitivity and higher storage of the excess glucose as fat.

Low-GI foods release their nutrients more slowly, meaning that insulin is released slower as well. Most of these nutrients then go into being used as immediate energy or to replenish glycogen stores, instead of for fat storage.

One problem that can occur through living a bad lifestyle and having bad eating habits is insulin resistance. If insulin is released in large quantities very often, the cells lose their sensitivity to it. This means that more and more insulin is always required to perform its function. At the extreme level, it can lead to a total loss of response and diabetes.


The loss of insulin sensitivity is one of the main culprits of obesity. One way this happens is because your liver loses insulin sensitivity as well.

One important function of insulin is that it tells the liver to increase production of glycogen. It also suppresses the liver’s capacity to produce new sugar. This process is called gluconeogenesis in fancy scientific language.

If the liver loses its ability to respond to insulin, the result is too much glucose (sugar) in the blood. This excess sugar then gets stored as fat and makes people put on more body fat.

Another important factor in reducing insulin sensitivity is the modern lifestyle. A bad lifestyle can cause several problems, including insulin resistance.

What many people don’t know, is that insulin can also be released without a person having to eat anything. This takes place when an outside stimuli causes the body to go into reflex mode. When this happens, the body starts releasing stress hormones such as adrenaline and cortisol.

These hormones then command the body to produce more sugars. In evolutionary terms, this was very beneficial, since stress hormones were released due to some dangerous outside stimuli. For example, a lion could be attacking or an enemy force could be heading your way.

In a moment like this you needed to be able to react quickly and with as much power as possible. So that’s why the body developed a mechanism to supply energy to its cells fast. Stress hormones gave a signal to the body, which then quickly released sugars in order to have more energy available to respond to these threats.

However in the modern world, stress is usually due to BS things like pressure at work, which puts the entire system out of whack. The body is constantly releasing sugars, causing the system to become more insulin resistant. The end result is that all that excess glucose gets stored as fat in the body, and people end up looking like Humpty Dumpty.


The Role of Insulin in Muscle Building

Insulin is needed for getting bigger and building muscles. Insulin is anti-catabolic. When it is present in the blood, it slows down the break-down of muscles proteins. Without insulin, muscle protein would start breaking down (in a process called proteolysis).

Insulin is also anabolic in that it aids the building up of muscles. It promotes protein synthesis and helps different nutrients (including amino acids) to get into the cells. In this way, they get different building blocks that they can then use to build bigger and stronger muscles.

Remember glucose is the basic source of energy for your body as well. Insulin helps in getting this energy-source to the right destination. When the different cells get the energy that they need, they can also work harder and longer, further enhancing the effect.

Also let’s not forget one little side-benefit, which has an impact on external aesthetics. Insulin saturates the muscles with amino acids and glycogen, which then gives them a fuller look.

So you see, insulin is incredibly important to how your physique will look like. Another important element that often gets forgotten, but is crucial for any budding Renaissance Man, is the fact that your brain is the biggest user of carbs and so insulin is needed for transporting glucose to the brain, not only to strengthen your willpower, but also to help you do all that thinking.

Read more:
What are carbohydrates?

Which nutrients are needed for your brain to function well?

In a future article, we will explore what types of strategies you can adopt to heighten insulin sensitivity and get a lean body. Stay tuned!


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One thought on “What Is Insulin And Why Is It Important For Building Muscle?”

  1. This is a very informative article. I love how you dwell deeper on the concept of insulin as well as its process in our body. I always associate Insulin and sugar as the main culprit in weight gain and obesity. While half of this claim is true, I cannot deny that stress is a major metabolism killer too.

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