Ketosis 101

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Don’t skip this article.  A lot of people don’t like to read a little more in depth on the science of Keto but I think it is important.  I do not think that you need to become an expert but I do think there is benefit in learning how and why you are eating the way you are.  This will make it easier to stay motivated and allow you to learn how the body works so you can continue to adjust the diet for different goals.

The basic definition of a Ketogenic Diet that you'll see almost everywhere is that it's a low carb high fat diet. The purpose of this low carb high fat approach is that you are trying to transition your body's primary fuel source from glucose to ketones.

Why is this Important?

When you are following a traditional standard American diet, one in which you are consuming a lot of carbohydrates, your body's primary fuel source is glucose.  When we consume carbohydrates they are broken down to glucose.  When glucose levels are increased, our pancreas will secrete insulin. Insulin will help drive this glucose into our cells so that it can be used for energy to help with the processes that need to take place in the body.

Glucose is also our primary fuel source because we are very efficient at using it.  If carbohydrates are available, then we will preferentially use them over any other available energy.  It is worth remembering that as a survival mechanism, the body loves to take the path of least resistance.

The problem is that we are discovering that chronic carb consumption and having constant elevated levels of insulin and blood glucose can lead to a lot of health issues, in particular, inflammation and insulin resistance.

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Insulin resistance, to put it simply, occurs when our cells lose the ability to communicate with insulin, to allow glucose to enter the cells effectively and produce the energy that is needed. This can lead to your cells essentially starving for energy.

Both Insulin resistance and inflammation are common contributors to conditions like diabetes, Alzheimer's, Parkinson's, cancer, PCOS, and many more.

It is becoming evident that consuming carbohydrates and having glucose as are primary fuel source long term, probably isn't the best idea for our health. This is where a Ketogenic Diet and ketosis can come in.

The purpose of a Ketogenic Diet is to provide a different fuel source. When we restrict carbohydrates, our body is very smart and is able to find a different source of fuel, which eventually leads to Ketosis.

What is Ketosis?

Ketosis: A metabolic state that is characterized by low levels of glucose and insulin and elevated levels of ketones.

Ketosis is simply a state where a new fuel source is being produced to make up for a lack of glucose. Note that I am referring to nutritional ketosis, which is NOT the same at the diabetic ketoacidosis we see commonly occurring in diabetics.

Ketosis is a completely normal metabolic process that we are all able to activate under the defined conditions of low glucose and insulin.  One of the reasons why this process exists is for survival.  Since ketosis kicks in when glucose and insulin is low, and it leads to the production of a different fuel source in ketones, it makes for an incredible survival mechanism to allow us to provide fuel for our brains and bodies during periods of food restriction or fasting.  Since the brain is unable to utilize just fat for fuel, it becomes increasingly important to be able to make another fuel source that the brain can use in ketones.

Ketologist Insight:

The Ketogenic diet, which also induces a state of ketosis because of its ability to also create conditions of low glucose and insulin, was founded for its ability to similarly mimic fasting.  This is what make Keto important, we can maintain a level of ketosis even after we have ate.

How Does Ketosis Work?

To reiterate, when we consume carbs we have an increase in glucose and insulin.  However, not consuming carb leads to decrease in glucose and insulin.  When we have low levels of glucose and insulin, our pancreas secretes another hormone known as glucagon.  Glucagon can interact with our stored fat, releasing it into the blood where it can be used as energy.

But the body doesn’t stop there.

Interestingly, while most of our body can run on fat for fuel, our brain cannot. Again, this is why we possess this unique metabolic mechanism of ketosis. The liver can break down fat and use it to make Ketones. Ketones are little molecules that can serve a big purpose in the body. 

Interestingly, the liver does not possess the necessary enzymes to use Ketones, so these little energy molecules are instead shuttled out of the liver and into the blood where they are able to travel to different cells and tissues in our body, particularly our brain. Research has found that the rest of the body tends to spare the use of ketones to safe them to be used by the brain.

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You can achieve an increase in blood ketones through something as simple as completing a short 16 to 18 hour fast.  After just a couple days of Ketogenic Dieting, you can experience ketone elevation enough to be considered “in ketosis”.  Being in ketosis means that you have a higher and more sustained increase in blood ketones. A lot of people want to know what the optimal range for being in ketosis is, the answer is that, we really don't know.

For some people it may be lower than for others.  It could also be different depending on your goal. We simply do not know enough to say what the optimal level is.  Really, the question should be whether or not you are Keto-Adapted?

What is Keto-Adapted?

Keto-Adaptation: A state that occurs when your body has become efficient at burning fat and producing and utilizing ketones for fuel.

Just being in ketosis does not mean that you are Keto-Adapted.  It is important to realize that our body has not been using fat and ketones for fuel for a long time, for most people not since they were babies.  For this reason, the cells in our body must up-regulate the processes necessary to take in ketones and use them as fuel.  Typically, this takes a little longer than just the production of ketones. This is why you may see a lag time from when you start a seeing your body producing ketones and when you actually start to feel some of the benefits of ketosis and this period is what we refer to as the Keto-Adaptation period.

Ketologist Tip:

The next common question is how to know if you are Keto-Adapted.  Since we don’t know the optimal level of blood ketones, there is really no sure-fire way of testing.  One of the things I always tell people is, rather than stressing about where your ketone levels need to be, you should do a self-assessment.  Ask the questions:

-          Do I have energy?

-          Am I hungry?

-          How is my sleep?

-          Am I seeing progress?

-          How is my workout performance?

If you are Keto-Adapted, you are likely experiencing some of these noticeable changes but this is not going to occur at first. When you first start a Ketogenic Diet, you can suffer from several different symptoms, things we refer to as the Keto Flu.

What is the Keto Flu?

The Keto Flu: Flu-like symptoms that can accompany induction to a Ketogenic Diet

The Keto Flu can occur during the Keto-Adaptation period.  One of the reasons for some of the symptoms of Keto Flu is due to the fact that we are not providing our bodies with its typical fuel source (glucose) but our bodies are not yet primed for using fat and ketones for fuel.  This can lead to things like mental fog, fatigue, and even feelings of depression and anxiety for some.

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However, it is important to point out that there are many strategies that you can take to manage your Keto Flu symptoms or for some, avoid them all together.  Check out my 7 Steps to Starting Keto for more!


The truth is, Ketosis is a lot more in depth than what I have tried to simply describe here.  It is a complex process that is still being studied everyday to learn more about optimizing it and all of its implications.  However, this general overview should provide you with enough insight to better understand the changes that are occurring in your body!

Christopher Irvin