Fuel v energy…  What exactly are ketones & where do they come from?

Questions like this are never easy to answer. The explanations involve a lot of long, confusing words, which then themselves require definition. As I have no medical or dietary training; all I can do is try and present the results of my own reading in as clear and jargon-free way as possible. If readers’ comments can help guide my understanding, then all feedback will be gratefully received!

The below represents my own explanation of the process. I hope it helps fill in a few gaps; for what can be a tricky thing to get your head around!

We’ve already touched on the metabolic state of ‘ketosis’ in an earlier blog. But what exactly are ketones? If they promise so much, we ought at least to understand a little about them.

As we’ve seen, ketosis is a state where the body’s energy-supply comes from ‘ketone-bodies’ in the blood. This is in direct contrast to a carb-fuelled metabolism, where energy is provided by glucose. That state is termed ‘glycolysis’.

So ketone-bodies are what we burn in ketosis; but where do they come from?

In order to produce ketone-bodies, the liver’s stores of glycogen must be depleted. This is achieved through restricting your intake of dietary carbohydrate.

Glycogen is the energy-source which the body creates from glucose in the food we eat. To understand the difference between glucose and glycogen, just think of an old-fashioned coal power-station.

Coal is burnt to produce heat. That heat turns a generator, which then generates electricity. It’s the electricity which powers our homes, not the coal itself. Think of glucose as the coal (our fuel). The body converts it to glycogen, which represents the electricity (our energy). It’s the glycogen which actually powers our muscles and organs; glucose is the fuel which we process to produce that energy.

So, we restrict our glucose-intake. The body then can’t produce glycogen, which has hitherto been our primary source of energy. Our bodies then face two choices. We can either die, or we can find another source of energy to replace the glycogen. This is what ketone-bodies are; the alternate source of energy our bodies manufacture when they can’t produce glycogen.

The name for the body’s production of ketone-bodies is ‘ketogenesis’. But how does the body produce them?

Ketones are produced primarily in the mitochondria of liver cells. Mitochondria are the parts of cells which generate the energy required for those cells to work. In our power-station, mitochondria represent the generator which turns the fuel into energy.

If glucose is required to make the energy-form glycogen; what is the body’s fuel-source which enables us to produce ketone-bodies? The answer is fatty-acids.

The term ‘ketone-bodies’ may be misleading. ‘Bodies’ implies that they’re solid. In fact, they’re water-soluble. When fatty-acids are broken down for energy, they produce ketone-bodies which can then power the brain and muscles.

These ketone-bodies come in three forms:

  • Acetone (the word ‘ketone’ actually derives from the old Germanic Aketon, meaning acetone)
  • Acetoacetic acid
  • Beta-hydroxybutyric acid (sources state this isn’t strictly a ketone, but it does the same thing, so I include it here).

It’s interesting to note that two forms of ketone-bodies are acidic. If levels of these become too high, the body enters a state of ketoacidosis. This is the poisonous ‘acidic’ state that type 1 diabetics enter when their bodies cease to produce the insulin required to process glucose from the food they’re eating.

Because the body can’t produce energy from that glucose, ketosis occurs which burns stored body-fat. When this is depleted, the body moves onto muscle-tissue in its desperate quest for energy. At this stage, ketosis turns into ketoacidosis. Un-metabolised glucose continues to build up in the blood, which then literally becomes poisonous. The results can be fatal if left untreated.

So if ketone-bodies are produced from fatty-acids, where do the fatty-acids come from?

Fatty acids can come from the food we eat, or from the body’s stored fat-reserves (body-fat). This is why you lose so much weight on a ketogenic-diet. Your body literally turns into a fat-burning machine, fuelled by the ready source of body-fat most of us have built up through excessive consumption of carbohydrate.

This makes ketosis an incredibly efficient source of energy. The body’s fat-stores are a huge fuel-tank, just waiting to be tapped. Because fatty-acids are also present in the food we eat, it’s practically impossible for that fuel-tank to run empty. This is why many athletes are turning to a ketogenic-diet: they don’t suffer the roller-coaster of energy peaks & troughs which result from burning glucose as fuel (more in that in another post).

So that’s a short explanation of where ketones come from, and how our body produces them. My brain has burned a fair few ketones, in trying to understand this process; so enough for now!

I hope you find this helpful and informative in trying to decipher the jargon.

Thanks for reading,



5 thoughts on “Fuel v energy…  What exactly are ketones & where do they come from?

  1. Pingback: Sugar-Cravings on a Low-Carb Diet – can you do LCHF with a sweet-tooth…? | country walks in ketosis

  2. Pingback: The role of salt in a ketogenic-diet. ‘Keto-Flu’ explained! | country walks in ketosis

  3. Pingback: New Year’s Diet? Why not try the ketogenic plan? Lose weight & become a fitter, happier, healthier ‘you’! | country walks in ketosis

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