The Keto diet has made ketones a buzzword, and people are buying measurement devices to find out if they are in ketosis or not. Manufacturers are making MCT oil supplements so that you can add exogenous (externally taken) ketones to your diet to immediately get some of
the keto magic.
But is all this really necessary to get the benefit of a keto lifestyle?
When your body is "metabolically flexible", it can switch over from primarily using glucose for energy to primarily using fatty-acids. In other words, your body can use up your body fat to produce energy.
Here is my understanding of the process.
Firstly, your body will use glycogen (stored form of glucose) in your muscles and some fat at a ratio of about 80% glycogen, and 20% fat or maybe less depending on your personal conditioning. As the glycogen in your muscles depletes you begin to use glycogen from your liver. At this time, it is the hormone glucagon which is stimulating the liver to convert glycogen back to glucose and release it into the blood, then as the level of glucose in your blood reduces further it will get to a point when you must eat more glucose, or, switch over to using a much higher level of fatty acids for immediate energy.
If your insulin level is high then the availability of any stored fat is limited and messages begin to be sent that you are ‘very’ hungry. When your body is not accustomed to providing a high level of fatty-acids for fuel, but energy demand is high, this is the time you can ‘bonk’ as your body struggles to oxidize fat fast enough to meet the current energy demand.
Experimentation with people on ketogenic diets has shown that in non-keto-adapted people, fat oxidation may occur at maximum rates as low as 0.2 grams per minute while in highly fat adapted athletes the rate can be as high as almost 2 grams per minute.
If you are metabolically flexible then the transition to fat-burning is seamless because your body can oxidize the fat at the level it is needed for your energy demands. It will use any fatty acids in circulation in your blood which will be actively replaced by fatty acids coming from your digestion process. As this level decreases it then seeks body fat to meet the demand. If your insulin level is low enough, the gates are opened and body fat will be consumed for energy.
When fatty acids are oxidized (burned up) by the mitochondria for energy, Ketones are the by-product of an incomplete oxidation of these fatty acids. This means that even if you are not producing measurable ketones, you can be burning fatty acids (or your body fat) and reducing your weight. If you are becoming ‘fat-adapted’ (becoming metabolically flexible) in the early stages of limiting glucose, then your body is learning to oxidize fat and the process can be less efficient initially resulting in a higher level of ketones being produced and this level can drop over time as your body adapts. This phenomenon can confuse some people testing for ketone levels, who see the level of ketones drop and become confused about why this is happening.
Muscles also adapt over time to the fatty-acid / ketone mix, becoming less dependent on ketones and more able to function on fatty acids directly. This change then allows ketones to be used by your brain as fuel. This is a preferred fuel for the brain, and is believed to be very helpful for people who have developed early stages of Alzheimer’s.
The shift in fuel for the brain from glucose to ketones is believed to be responsible for the thinking clarity that people comment on when using a ketogenic diet. It is these types of adaptions that take weeks of change to adjust to and why the shift to fat-adaption takes some time, usually quoted at about 3 weeks minimum.
There are 3 different ketones produced, mainly in the liver, by the metabolism process.
Acetoacetate is the first ketone produced by your liver with the others produced from this. The ketones in your urine are acetoacetate and these are being excreted so are not a true measure of the ketones in your blood. The ketones you measure in your blood are predominantly Beta-Hydroxybutyrate which is the most important for energy and is anti-inflammatory. The ketone you measure in your breath is acetone, which is a by-product of ketone production.
It is important to understand that you do not need to be on a Keto diet to have ketones in your blood. Other diets or even the combination of what you are eating and doing can create the conditions for ketones in your blood. Healthy baby humans are born ‘chubby’ and this body fat is used up in the early months by the baby in a state of ketosis to help with brain development. Human mothers breast milk is 48% saturated fat and this is also used by the baby for growth and development, producing ketones.
You don’t need to know all this. Just using a tape measure to see your waist measurement reduce and finding that you almost never feel hungry, can tell you that you are burning fatty-acids for fuel and producing ketones.
George Elder, Author, "Take Back Your Health", Amazon $3.99.