Carbs, Insulin, and Bodybuilding. How does it work?

The role of insulin is a current topic reverberating through gyms everywhere. Insulin is a hormone best known for its role in glucose metabolism. In an attempt to provide some clear scientific information to our trainers, this article will discuss the different classifications of carbohydrates, and how the body regulates blood glucose levels. Practical applications to bodybuilders will close out the article.

Carbohydrates 

Carbohydrates provide direct energy for the human brain, central nervous system, and muscle cells in the form of glucose (blood sugar). Carbohydrates can be broken down into simple carbohydrates or complex carbohydrates.

Simple Carbohydrates are sugars, organic compounds whose bonds are easily broken down by digestion. Sugars are classified as monosaccharides (mono = one), or disaccharides (di= two). Monosaccharides include glucose, galactose, and fructose. Disaccharides are two monosaccharide units linked together and include maltose (two glucose units), sucrose (fructose plus glucose), and lactose (galactose plus glucose). Your body only has the ability to absorb monosaccharides into the blood.

Complex carbohydrates are defined as polysaccharides (poly = many) that are found in starch and fiber. Starches are polysaccharides humans can digest, but must be broken down into monosaccharides before they can be taken into the blood. Polysaccharides are either linear (amylose-polymer of 400 to thousands of glucose) or branched (amlyopectin-polymer containing hundreds of glucose). Glycogen (stored glucose within the muscle), is similar in structure to amylopectin, and will be discussed later in bodybuilding applications. Cellulose is fiber within vegetables which humans are unable to break down and absorb into the blood.

How the Body Uses Carbohydrates 

The body, after digestion and absorption through the walls of the small intestines, can put glucose to work in three ways.
It can burn the glucose immediately within mitochondria, releasing carbon dioxide, water and energy.

If the glucose is not needed immediately, it is converted by the liver or the muscles into glycogen. Muscle glycogen provides energy only to muscles. Liver glycogen can supply energy to any part of the body.

Any glucose left over after glycogen saturation is converted to fat by the liver, and stored in adipose tissue around the body. The degree and pattern of fat buildup depends on an array of factors, but are primarily linked to whether a person consistently consumes more calories than are burned through activity.

Blood-Sugar Connection 

The body's natural regulatory system automatically maintains close control over the level of blood glucose. The body has approximately 20 grams of blood borne glucose circulating continuously. If blood sugar increases then the pancreas releases insulin. If this level is too low than glucagon is released.

Pancreas
Monitors blood glucose concentrations If blood glucose level is too high Insulin is released... If glucose level is too low Glucagon is released

Signals Signals

Fat and muscle cells to Absorb glucose liver to break down glycogen and release glucose to the blood
thus lowering blood glucose to normal levels thus raising blood glucose to normal levels
Happens right after a meal Happens between meals
Note: Muscle glycogen does not provide glucose to the blood. Muscle glycogen is used only by muscle tissue.

Bodybuilding Applications 

It is important for bodybuilders to understand that when insulin levels are high your body will store excess glucose as bodyweight. Unfortunately, your body does not care if it is muscle weight or fat weight. It is important to realize the difference in carbohydrates and their use by muscle tissue. Enzymes within muscles readily metabolize starch, which is broken down into usable glucose. The liver has the intermediary enzymes to convert glucose, fructose, galactose, amino acids, and other metabolites for its glycogen stores. Since your muscles have the ability to store 250 to 400 grams of glycogen and your liver only has the ability to store 100 grams of glycogen, it is advisable to keep a high proportion of your carbohydrate calories from complex sources. As mentioned earlier, muscle glycogen is only used by muscle tissue. Since muscle glycogen is similar to an amylopectin as in starch, it is logical to supply your body with complex carbohydrates to replenish muscle glycogen stores.


At first glance carbohydrates and insulin can be a confusing topic and if left to the rhetoric of the average gym can spawn into a deluge of misinformation. We hope that the article served to clarify some of the confusion surrounding carbohydrates and insulin.