What is Ketosis?

Ketosis Introduction

According to Google Dictionary, Ketosis is defined as, “a metabolic state characterized by raised levels of ketone bodies in the body tissues, which is typically pathological in conditions such as diabetes, or may be the consequence of a diet that is very low in carbohydrates.” Although this definition is a good starting place, let’s break it down in order to get a better understanding.

Ketosis is in fact, “a metabolic state that is characterized by raised levels of ketone bodies in the body tissues.” In other words, when the body is in a state of ketosis it will use “ketone bodies” for energy.

If this is the first time hearing about ketosis, you are probably wondering what a “ketone body” is. However, we will save that topic for later in this discussion. Just know that ketosis is a totally different metabolic state. Rather than using glucose, you are using ketone bodies.

For now, we will focus on metabolism and consider how the metabolism of fats into ketone bodies differs from the more well known metabolism of carbohydrates. It gets a little “nerdy and sciency.” So if you are only interested in the basics, we have a summary:

  • Eating mainly fat for fuel changes the motor of your body.
  • Fat breaks down into ketone bodies.
  • Your cells use the ketone bodies (instead of glucose) for energy.
  • You repair major parts your body through this metabolism.

Science behind ketosis

As you may already know, carbohydrates (or complex sugars) are the first source of energy the body will use when available. When you have a steady intake of carbs, your body will use them first. It is the “default metabolism.”

So what happens when you eliminate the intake of carbohydrates?

The simple answer is that your body must metabolize a different source of energy. Your body will switch from metabolizing sugars to metabolizing fat. Your body is always metabolizing fat, but it does it in a different way now. It breaks them down through different pathways as a direct result of carbohydrate restriction.

This is known as “ketosis.” Now it starts to get a little technical, but please bear with us. You will be a master at understanding this in no time.

Let’s get technical

The most important compound for your body to produce energy is acetyl CoA. Acetyl CoA is the compound that feeds the Citric Acid Cycle and is responsible for producing the majority of your body’s energy. Both carbohydrates and fats will break down into acetyl CoA.

The pathway of red arrows (in the picture below) show that carbohydrates will first break down into glucose. Then it undergoes glycolysis, where glucose breaks down into pyruvate. Lastly, it will undergo pyruvate oxidation – where pyruvate oxidizes into acetyl CoA.[1]

Fats on the other hand as the pathway of green arrows, will undergo lipolysis where they are broken down into free fatty acids (FFA), then these free fatty acids undergo fatty acid oxidation where they are broken down directly into acetyl CoA.[2]

At this point we have only discussed metabolism of each substance. This is not ketosis yet. Both of these pathways occur when you eat a non-ketogenic diet. You may be confused about where the previously mentioned “ketone bodies” come into play. The formation of ketone bodies are the true beauty of ketosis and the reason it is so efficient as a means of producing energy.


There are three molecules that are referred to as “ketone bodies”: beta-hydroxybutyrate, acetoacetate, and acetone. Unlike the metabolism of glucose, during ketosis there is no way for the body to regulate the production of acetyl CoA by slowing down lipolysis or fatty acid oxidation. Therefore, there becomes a build-up of acetyl CoA in your system, and your body does not want to waste this precious energy molecule.

Instead of regulating the production of acetyl CoA, the body will synthesize extra acetyl CoA into the ketone bodies as a way to store the energy. Unlike acetyl CoA, acetoacetate and beta-hydroxybutyrate are water soluble. So they will be able to enter the bloodstream, travel through the body, and be used as energy where and when they are needed. The body can easily break acetoacetate and beta-hydroxybutyrate back down into acetyl CoA. Then it goes into the citric acid cycle and produces energy. Lastly, when acetoacetate and beta-hydroxybutyrate are metabolized, acetone is released as a gaseous byproduct much like how carbon dioxide is released during the metabolism of carbohydrates and therefore acetone is exhaled when in ketosis.[2][3]

Summary of ketosis

Here are the main takeaways:

  • Your body will use carbohydrate as its first source of energy. Fats will be used to a lesser extent.
  • Ketosis occurs when your body primarily relies on fat for energy. This happens when you restrict carbohydrates.
  • Carbohydrates and fats eventually break down into the same molecule, acetyl CoA. This provides your body with the vast majority of its energy.
  • When in a state of ketosis, your body will naturally turn all the extra acetly CoA into ketone bodies.
    • These are able to travel through your bloodstream to be used as energy wherever and whenever needed.
  • A state of ketosis will bring down your blood glucose levels while at the same time reducing your body fat.
    • You are in a state of constant fat metabolism.

Ketosis And Diabetes

By now the last piece of the definition which reads, “may be the consequence of a diet that is very low in carbohydrates,” should be apparent. When the body is lacking a steady intake of carbohydrates, it will resort to a state of ketosis as a method of sourcing energy.

Yet, we must still address what the definition means by, “which is typically pathological in conditions such as diabetes.” Through this discussion we will also introduce a great benefit to Ketosis.

Diabetes is a disease in which a person either:

1) does not produce the right levels of insulin (Type 1)

2) does not respond to the insulin (Type 2)

Insulin is hormone that allows your body to use sugar for energy or to store glucose for future use. Insulin helps keep your blood sugar level from getting too high (hyperglycemia) or too low (hypoglycemia).[4] When the body’s production of insulin gets low enough, the body will not be able to get enough energy from carbs, and it will be a natural reaction for the body to begin breaking down fat for energy.

The metabolism of ketone bodies as a response to a low insulin levels causes diabetic ketoacidosis (DKA) which is NOT ketosis. DKA causes the acid levels in blood to rise above healthy limits. The body does not function properly. This is not to say that a diabetic cannot go on a ketogenic diet! You can enter into a controlled state of ketosis that will not trigger ketoacidosis.[5][6] We call this “nutritional ketosis.” It is very easy to maintain, and you will never have to worry about getting DKA.

Managing diabetes

A person with diabetes needs to monitor their blood sugar to make sure it does not rise too high or fall too low. If you experience hyperglycemia (high blood sugar), you usually take insulin to bring the blood sugar down. If you see hypoglycemia (low blood sugar), you usually eat sugar to bring it back up. Each state, hyper or hypo, are bad for an individual’s health.

However, hyperglycemia can definitely be more of a pain. The delivery methods, such as injections, of insulin are more invasive. It is also very costly. A way to maintain low blood sugar without insulin may be an appealing idea to many diabetics. Having too much insulin causes its own problems, too (check out why). So, we are really tackling two problems at once.

This is where using the ketogenic diet and the ketogenic lifestyle can be extremely useful. If you are interested in learning more about this subject we suggest signing up for our Starter Guide and Newsletter. We would love to help you along your journey!


In conclusion, ketosis is a state in which the body uses fat metabolism as its main path for energy. During Ketosis you produce the same molecule that is produced during carbohydrate metabolism. But you get more of it, and you do not raise your blood sugar to do so. Ketosis is very beneficial to the body. It lowers blood glucose levels, decreases body fat, helps mental function, and a wide variety of other benefits.

We hope you learned something new. Ketosis is not just the result of some popular diet. It is a totally different therapeutic metabolism. Hopefully it sparked your interest in the ketogenic lifestyle.

For more information on ketosis please visit the links below!


[1] Campbell, NA, et al. (2017). Campbell Biology in Focus. Pearson Education Limited.

[2] Laffel L. (1999). Ketone bodies: a review of physiology, pathophysiology and application of monitoring diabetesDiabetes/Metabolism Research and Reviews 15(6): 412-426.

[3] Barnett CR, Barnett YA. (2003). Ketone BodiesEncyclopedia of Food Sciences and Nutrition(2nd ed.) pg. 3421-3425.

[4] Hess-Fischl A. “What Is Insulin?” EndocrineWeb. Vertical Health. [Online]. Available: www.endocrineweb.com/conditions/type-1-diabetes/what-insulin. Accessed: 14 May 2018.

[5] “Diabetic Ketoacidosis (DKA) – Topic Overview.” WebMD. [Online]. Available: www.webmd.com/diabetes/tc/diabetic-ketoacidosis-dka-topic-overview#1. Accessed: 14 May 2018.

[6] Shifflett T. (2017). “Can You Manage Your Diabetes On A Ketogenic Diet?”TheDiabetesCouncil.com. [Online]. Available: www.thediabetescouncil.com/can-you-manage-your-diabetes-on-a-ketogenic-diet/Accessed: 14 May 2018.

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