What is ketosis? How does it work?

When the body enters a state of ketosis, a remarkable transition occurs in how energy is used and stored. Instead of relying on glucose as its primary fuel source, i.e. sugar burning, the body switches to burning fat, and produces ketones as an alternative fuel.

This is a natural condition that occurs when there is an absence of carbohydrates over time.

This process not only changes how our energy is produced og can be used, but also affects how the body handles excess energy.

What is sugar burning? All carbohydrates are a form of sugar, just in a different form than the crystals we know from table sugar. Starch, for example, is just "flat-packed" sugar, which starts turning into sugar as soon as it comes into contact with your saliva.

Insulin vs. Glucagon: Who controls the energy balance?

In a glucose-based metabolism, i.e. the modern diet with lots of carbohydrates, insulin the dominant hormone. Insulin ensures the storage of energy, either as fat or glycogen, and inhibits the release of stored energy. Glucagon, on the other hand, has the opposite effect: it promotes fat burning and the release of energy.

Insulin builds up, and glucagon breaks down.

In ketosis, where carbohydrate intake is very low, insulin levels are significantly reduced, and glucagon takes over as the leading hormone. This creates a hormonal state that favors fat burning and ketone production, while minimizing energy storage. In cases of increased energy intake relative to what we are currently using, the body can waste this energy, instead of storing it as fat on the body, and in and around organs.

What happens to gluconeogenesis – the formation of glucose in the liver?

gluconeogenesis is the body's process of producing glucose from non-carbohydrate sources, such as from proteins (amino acids). However, this process works very differently depending on the body's metabolic state:

In a glucose-based state: When the body relies on glucose for energy, it will rapidly break down proteins into amino acids to produce glucose, if the supply of carbohydrates becomes temporary too low. The body's perception of needing glucose is heightened, because glucose is the primary source of energy. The body therefore tries to produce these amounts as soon as it does not get them from food. This can lead to muscle loss and inefficient energy use.

The transition from sugar burning to ketosis can be a bit tough, because there will actually be a shortage of both glucose and ketones. You are in a kind of metabolic limbo for a few days, before the liver picks up the pace of making ketones instead.

Gluconeogenesis in ketosis: Gluconeogenesis is very limited, because the body has a significantly lower need for glucose. The brain, which previously required a lot of glucose, switches to using ketones as fuel. This saves protein and reduces the need to break down muscle tissue. Gluconeogenesis is an expensive process for the body, so it does not carry out this unless there is a real need. The blood's need for its measly 4 grams in homeostasis, is easily maintained by the liver.

How the body "wastes" energy in ketosis

One of the most interesting aspects of ketosis is how the body handles excess energy. Instead of storing all excess energy as fat, the body has several mechanisms to get rid of it:

Ketone excretion: When ketone production exceeds needs, the body excretes the excess through urine and breath. This explains why people in ketosis often experience “ketone breath,” which some compare to the smell of nail polish remover or glue. This goes away when production stabilizes.

Increased heat production: In ketosis, thermogenesis is stimulated, a process in which energy is released as heat instead of being stored as fat. This occurs, among other things, in the body's brown adipose tissue.

Lower efficiency in fat storage: Without high levels of insulin, which normally drives fat storage,
the body less efficient at storing fat, even in a calorie surplus.

Higher energy consumption: The process of breaking down fat and producing ketones is energy-intensive, which increases the body's total energy expenditure.

Increased activity: Many people spontaneously experience increased energy in ketosis, and you are unconsciously more active, which contributes to higher energy expenditure. You get increased initiative to get things done, and you have less need for rest.

Increased fat intake: When we eat more fat, the bile that breaks down the fat will stop being released when the body thinks it has dissolved enough fat for energy. The rest of the fat will be sent untreated out of our sewage system, and you may get some loose stomach. By adjusting the amount of fat you eat, this will be corrected, and you will achieve a balance in your intake that matches your energy expenditure.

A natural, evolutionary adaptation

Ketosis represents an evolutionary mechanism that allowed humans to survive periods of food scarcity, i.e. fasting. But not least, the ability to ketosis was useful during a nearly 3 million year long ice age, when fruits and vegetables were not available.

By reducing our reliance on carbohydrates and utilizing fat stores more efficiently, our bodies could sustain energy without damaging essential tissues like muscles and organs. We are one of the very few animals that is specially adapted to thrive in ketosis, and many believe that the human animal thrives best both physically, mentally, and with a happy heart and happy brain, both of which love to live on ketones.

Modern research, led by experts like Dr. Ben Bikman, shows how this metabolic state can be used to improve health and weight management. By understanding the difference between ketosis and a glucose-based metabolism, we can learn to harness the body's natural ability to balance energy and maintain a healthy metabolism.

SOURCES

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