How Ketones are Formed in the Body

How Ketones Are Formed

How Ketones are Formed in the Body

In this article, I’m going to be explaining how ketones are formed in the body in the least scientific way possible. If you prefer, you can view the video here:

Table of Contents

What conditions are needed for ketones to be produced?

Low Available Glucose

Ketones are formed when there is low available glucose from our diets. If we consume low levels of refined sugar or starchy carbohydrates, which ultimately break down into glucose, we reduce the amount of glucose available in our bodies.

Empty Glycogen Stores

We need to have run out of glycogen, which is our short-term bodily energy store. It’s found in our muscle tissue and in our liver, and rapidly breaks down into glucose between meals in order to supply us with short-term energy. That store needs to have run out.

Low Insulin Levels

Insulin is our fat storage hormone. Basically, it shunts glucose out of the blood into fat cells in order for it to be stored as fat. We can think of insulin as a fat storage hormone.
how ketones are formed

Reducing Glucose and Insulin Levels

If we’re trying to access our fat stores in order to use them for energy so that we can lose fat, we definitely want to have low glucose levels and low insulin levels. So how are we going to do that?

1. Low Carb Diets

Particularly ketogenetic diets, which are very low carbohydrate diets – so called because our body creates lots of ketones. These diets mean that our intake of glucose either from sugar or from starchy carbohydrates is very low. It takes about two or three days to burn through those short-term energy stores in our bodies in order to get into a state of ketosis. That time period will vary for different people but that’s just a rough guide.

2. Fasting

The second way to achieve low glucose and insulin levels is fasting: simply not eating. You are likely to burn through your short-term energy stores probably in a day, maybe a day and a half in that situation.

3. Exercise

The final way of producing those conditions in the body is via exercise. Take marathon running, for example: you may have heard the term that marathon runners use called ‘hitting the wall’. This describes the sensation that people typically get at about mile 18, and that corresponds to the body’s glycogen stores running out. A runner who loads up on carbohydrates for a day or two before the race has full glycogen stores when they start the race, but they’ve run so far that they’ve just burned through those stores. These are people who are probably not used to running on ketones as their major source of energy, so when that happens it’s like running into a wall.
Under the conditions of low available glucose and low available insulin levels, fat can be very easily released from our cells.
Most cells in the body can use fat for energy but the brain can’t, so we need another trick up our sleeves, and specifically it’s our liver that really helps us out here.
How Ketones Are Formed
Our livers are awesome: they do an incredible job in our body of converting one thing into another thing and specifically, in this case, it’s turning fat into ketones.


Fat is released from the cells all over our body and is transported via our bloodstream into the liver: once there it’s turned into ketones.

That’s the process known as ketogenesis.

Once the liver begins to transform fat into ketones, the ketone levels will begin to rise in our blood and be transported around the body in order for our cells to use them.
Now, most of the cells in the body can run on three different types of fuels:-

  1. Glucose
  2. Fat
  3. Ketones

Our livers produce three different types of ketones.
The different ways we measure ketones all measure these different types.
I’ve made a separate video about the different ways that we can measure ketones, where I discuss the pros and cons of each method.

But beyond that, all you really need to know that the liver produces ketones.


Ketones are produced by the body when conditions of low available glucose and low available insulin levels are satisfied within the body and we can use fat from our cells. Some of that is turned into ketones in the liver, which can be used by our brain.

Now, when ketone production is up and running up to 70% of the energy needs of our brain come from ketones, and up to 50% of the energy needs of our entire body come from burning ketones.

It’s a really, really good alternative fuel source for the brain and the whole body.

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