What Are Ketones?

In a nutshell, a ketone is a byproduct of burned or metabolized fat. It serves as a better alternative energy source or fuel than carbohydrates (i.e. glucose).

Ketones are chemicals made in your liver, usually as a metabolic response to being in dietary ketosis.

Basically when your body runs out of stored glucose (both from what's in the bloodstream and stored as glycogen in muscle), the body can create the needed glucose from other available resources.

Your body can use and convert 5 different items to be used for fuel (in no particular order):

  • Carbohydrates

  • Fats

  • Proteins

  • Alcohol

  • Ketones

The one we are going to focus on is fat. When we "burn" fat for fuel we create ketones. But here's the kicker...ketones can be used for fuel as well.

But First...Insulin

Before we can talk about ketones and how they are produced we first have to understand, a little bit at least, about the role of insulin.

When carbohydrates (i.e., cake, cookies, rice, fruit, oatmeal, pasta, potatoes, etc.) are consumed, the pancreas releases insulin due to the elevation in blood glucose (sugar) levels. Insulin is a hormone that provides a signal for tissues to take up the excess blood glucose; the glucose is then either stored as glycogen or converted to and stored as fat.  Chronically elevated glucose levels circulating in the bloodstream are harmful and therefore, insulin protects our body from glucose-related damage.  However, when insulin levels are even slightly elevated, stored fat cannot be broken down and used for energy.  Also, dietary fat will be stored.

This is why insulin is considered our fat storage hormone. And if you are on a weight loss program, you have to keep insulin low and out of play, otherwise you will never tap into the stored fat on your body and burn it.

Let's recap real quick.

So here we have a fuel called fat and when we metabolize it we produce a thing called a ketone that also can be used for fuel. That's genius! Yes it is and your body, and most importantly your brain, loves and prefers to use ketones for fuel. Let's keep going!

You make ketones when you don’t have enough stored glucose (or sugar) to turn into energy. When your body senses that you need an alternative to sugar, it transforms fat into ketones.

You might think that you have to be on a ketogenic diet or be in a state of ketosis to have ketones in your bloodstream. The fact is you have ketones in you quite often. In fact, you might have ketones floating around in your bloodstream right now.

So, what’s the deal with ketones? What are they? And why would you want more of them?

Read on for a full overview of ketones and their role as the primary energy source once you’re in ketosis.

When Does Your Body Make Ketones?

Ketones, also known as “ketone bodies,” are byproducts of the body breaking down fat for energy. This only happens when your carbohydrate intake is low, and your body switches into a state of ketosis (1).

Carbohydrate Restriction

When you go super low-carb, fast for a prolonged period, or exercise heavily, your body eventually burns through glucose (aka, blood sugar) and glycogen stores (aka, stored sugars). Once glycogen is depleted, usually after the 1st or 2nd day of carbohydrate-restriction, fatty acids are heavily relied upon to fuel the tissues.  At this point, your body will start to break down dietary fat and body fat for fuel ⁠— a process known as beta-oxidation.

The brain, however, cannot directly use fatty acids for energy.  This is where ketone bodies come into play!

People following a ketogenic diet specifically reduce their carbohydrate intake for this reason: to create ketones for energy.

Many people use the benefits of ketosis — less reliance on carbs and more burning of fat — to possibly help lower blood pressure, reduce cravings, improve cholesterol, increase weight loss, improve energy, and more (2).

Types of Ketone Bodies

So, what else do you need to know? To start, there are technically three types of ketone bodies:

  • Acetoacetate (AcAc)

  • Beta-hydroxybutyric acid (BHB)

  • Acetone

Both acetoacetate and beta-hydroxybutyrate are responsible for transporting energy from the liver to other tissues in your body.

Acetoacetate is the first ketone that’s created.

Beta-hydroxybutyrate (BHB) is then formed from acetoacetate. (It should be noted that BHB is not technically a ketone due to its chemical structure, but it’s considered a ketone because of its relation to the other metabolites and its function in your body.)

Acetone, which is the simplest and least-used ketone body, is created spontaneously as a side product of acetoacetate.

If acetone is not needed for energy, it will break down and be removed from the body as waste through the breath or urine. Acetone is the cause of a characteristic fruity smell on the breath when someone is in ketosis or ketoacidosis.

This study shows how ketone bodies may improve brain health and function.

How Does Your Body Use Ketones?

Ketone bodies are water soluble unlike fatty acids, so they travel easily through the bloodstream to reach other tissues to be used for fuel.  The brain is an energy hog. Let's face it, it's doing a lot of work all the time to monitor and run your entire body. So it requires a lot of fuel (over 25%) in the form of oxygen and glucose. The brain uses ~100% glucose for energy when carbohydrates are present in the diet.  However, when ketones are present, the brain can derive up to 60% of its energy needs directly from ketone bodies. 

The liver can convert substrates like proteins into glucose (a process called gluconeogenesis) which can then fuel the other 40% of the brain’s energy during carbohydrate-restriction.

All cells have the capacity to use ketone bodies, except liver and red blood cells, however some cells prefer ketones.  Besides the brain, the heart and intestines also prefer to use ketone bodies for fuel.

The production and utilization of ketone bodies is thought to be a protective mechanism during times of famine as they increased survival time in starving individuals by providing a non-dietary source of energy.

In addition to providing a cellular energy, ketones have a plethora of associated health benefits. 

Some benefits include (but are not limited to):

  • Regulated energy levels

  • Reduced oxidative stress and inflammation

  • Reduced anxiety and depression

  • Improvements in conditions such as epilepsy, Parkinson’s disease, Alzheimer’s disease, polycystic ovary syndrome, diabetes, obesity, cardiovascular disease, and cancer

  • Improved body composition

Why Does Your Body Use Ketones?

For thousands of generations, humans have relied on ketones for energy when glucose isn’t  available.

For example, our ancestors likely experienced frequent periods when food wasn’t immediately available, whether because of food preparation or availability.  And still today, our bodies are amazing at adapting to the burning of ketone bodies for fuel.

Other functional benefits of ketones can include:

  • An increase in mental performance — because ketones readily cross the blood-brain barrier to provide your brain with quick and efficient fuel (3).

  • Physical energy — once you’re not relying on glucose for fuel, your body will become more effective at burning fat during exercise. This means more fat burning and steady energy once you’re in ketosis (4).

Exogenous vs Endogenous Ketones and Supplementation

First off, there are exogenous ketones and endogenous ketones. Exogenous simply means from outside the body. Endogenous simply means from inside the body. Meaning our bodies produced it.

Individuals may elevate circulating ketone bodies by fasting long-term or chronically restricting dietary carbohydrates, as mentioned above.  If those ketone-producing strategies are not feasible to maintain as a lifestyle, ketones may also be consumed in order to elevate blood ketone levels. 

These are called “exogenous ketones” because they are made outside of the body whereas “endogenous ketones” are made inside the body in the liver. 

Studies have shown success with using exogenous ketones as a therapy for certain conditions in infants and adults.  Ketosis, or elevated ketone levels, has become a hot topic in the nutrition, health, and athletic performance fields, and rightfully so.

With the positive outcomes that both a very low carbohydrate, ketogenic diet and exogenous ketones are demonstrating, researchers are hopping on board to study how ketone bodies affect various aspects of health and human performance. 

It is an interesting decade for nutrition, as ideas on “good nutrition” seem to be dramatically shifting and the shift seems to be in favor of carbohydrate-restriction due to the associated ketone body production.

Final Thoughts

Carbohydrate consumption causes blood sugar levels to rise, subsequently raising insulin levels. Insulin prevents fats cells from entering the bloodstream to be used for energy, so it remains stored in the body. When you lower your intake of carbohydrates, blood sugar and insulin levels drop, causing your body to look for an alternative energy source. Excess glucose that has been converted to glycogen is depleted after1-2 days of a carb restricted diet, then it turns to fat storage. Entering the metabolic state known as ketosis, your body begins to utilize ketones, the energy source produced by the liver as it breaks down fat. To maintain a ketogenic diet is done so with a HIGH FAT, low carbohydrate diet. This can be difficult for some, so the supplementation of exogenous ketones is a healthy alternative that can help you maintain a higher level of ketones in your body while still reaping all of the benefits ketones have to offer!

If you'd like to experience all the benefits of exogenous ketones and see the results first-hand visit:


The Experiment

In this video I put Pruvit's Exogenous Ketones to the test. Check out my results.


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