What is Ketosis? Stages, Benefits, Side Effects & Measure

what is ketosis

Ketosis is a metabolic state of the body in which it gets energy from ketones in the blood. This is in contrast to a state called glycolysis, in which glucose provides the energy. Ketosis is generally said to occur when the body metabolizes fat at a high rate, in the process of converting fatty acids into ketones. Most people enter ketosis when they limit their carbohydrate intake or fast for several days. Moving further in this article, we will understand what is ketosis in detail along with its benefits and side effects.

What is ketosis?

When following a keto diet, ketosis becomes the resting state of the body. It impacts not only how energy is produced, but what ends up producing this energy.


The body takes up carbs (bread, fruit, grains, starchy vegetables, etc.) as the source of energy either through the diet or through glycogen, which is how sugar is stored in the body. And as long as there are enough carbs available, the body does not enter ketosis, preferring it only as an alternative method of generating energy.

In ketosis, energy is produced from ketones in the blood. Ketones have many properties that distinguish them from sugar as being a source of energy. Sugar does not burn as efficiently as ketones do. Plus, ketones also increase the efficiency of the cells as they produce energy.

If we consider an evolutionary perspective on sources of energy for the body, we see that ketones are an essential alternative to glucose.

According to Chris Masterjohn, Ph.D., our ancestors evolved the ability to burn ketones as a source of energy so that they could preserve muscle mass while sustaining brain functioning when food was scarce.

Setting the stage for ketosis – ketogenesis, and gluconeogenesis

A biochemical process called ketogenesis activates ketosis as a metabolic state. Ketogenesis is carried out minimally, mostly in liver cells, to provide the heart and renal cortex (the part of the kidney in which ultrafiltration occurs) with ketones for energy.

However, the change in metabolic states – from glycolysis to ketosis – is not achieved without the intermediary process of gluconeogenesis.

Understanding gluconeogenesis

Gluconeogenesis is one of the many processes used by the liver to keep blood sugar levels steady. When the body has burned through all the glucose in the body, the liver starts the breaking down process of the glycogen (the stored form of glucose) in the body.

It also facilitates gluconeogenesis as a new process to provide the cells with sugar. In this process, the fat cells start to release fatty acids into the blood, a process called ketogenesis. But the primary source of energy remains gluconeogenesis.

Should there not be enough carbohydrates in the blood, the liver continues to break down the already stored glycogen. Through the use of gluconeogenesis, the body continues to receive energy even when no new carbs are coming in.

After about 6 to 24 hours of limited carbohydrate intake, the glycogen reserves of the body get depleted. As a result of this, the body switches to gluconeogenesis as the primary process through which energy is produced.

The transition into ketogenesis

When there is not enough glycogen in the body, and when the liver doesn’t have enough energy to maintain gluconeogenesis for the whole body, ketogenesis increases to produce ketones for muscle, heart, and brain cells.

As a process, ketogenesis can provide energy for all parts of the body except for the liver cells and the red blood cells. Thus, gluconeogenesis and ketogenesis always go hand in hand; the only differentiating factor being the degree to which these processes are producing energy.

During ketogenesis, fatty acids and amino acids, such as lysine and leucine, convert into acetoacetate. Acetoacetate further turns into either acetone or beta-hydroxybutyrate (BHB).

Once your body is in ketosis, all these ketones are used by your body as a source of energy. However, acetone is not found in abundance within our body.  You must follow a ketogenic diet plan on a regular basis to get sufficient acetone.

Adapting to ketosis

It takes up to a week or more for the body to get accustomed to the new processes that become responsible for the production of energy. In ketosis, the body no longer uses sugar or glucose as the primary source of energy and instead, starts to use fat as that source.

As one’s cells become accustomed to having minimal carbohydrates, more and more of the body’s energy requirements are served by ketones (2). In fact, when you have become keto-adapted, up to 50% of your daily physical energy needs and 70% of the brain’s energy needs may be met by ketones (3)!

As a result of this, your body can preserve muscle mass as well as maintain brain functioning while you achieve all the health benefits of ketosis!

As a result of keto-adaptation, more mitochondria are created in the ketone burning cells. Moreover, the mitochondria that already exist in those cells also become more efficient by upregulating enzymes which help in the metabolism of ketones.

It is due to these changes that our bodies can return to ketosis again after consuming carbohydrates. If you want to maintain ketosis for long periods of time, it is suggested that you must follow a ketogenic diet.

While other methods, such as intense exercise and fasting (4), are quicker and temporarily more effective but they cannot maintain the state of ketosis for long. But following a keto diet is by far the healthiest way to keep ketosis for an extended period.

Summarising ketosis

Ketosis is a unique metabolic state which is activated once blood ketone levels reach a certain level. The state of ketosis is achieved when ketogenesis takes place in the body, forming ketone bodies from fatty acids and ketogenic amino acids.

It is surmised that ketogenesis evolved as a way for humans to maintain muscle mass while providing their hungry brains with energy when there was a lack of food all around.

Humans can efficiently burn ketones for fuel and can also experience many health benefits as a consequence. To achieve ketosis, we must go through specific metabolic processes before our ketone levels can increase. The stages that the body goes through are as follows:

Phase 1 (Glycogen depletion phase)

During this phase, glucagon levels increase while insulin levels decrease. It usually lasts between 6 to 24 hours once the body severely limits its carbohydrate intake. Here, the liver breaks down the already stored glycogen and increases gluconeogenesis as an energy-producing process.

Phase 2 (Gluconeogenic phase)

This phase lasts roughly 2 to 10 days of limited carbohydrate intake. Here, the glycogen is fully depleted, and gluconeogenesis becomes fully responsible for producing energy in the body.

The time duration window for this phase is quite broad because its length varies from person to person, depending on who is fasting. Healthy males, as well as sedentary individuals, tend to stay in this phase for much longer than healthy women.

Phase 3 (Ketogenic phase)

This phase begins roughly at the same time as the gluconeogenic phase. During it, fat and ketones are increasingly used to produce energy, as opposed to proteins and glucose. Once you have reached this phase, you are definitely in ketosis.

Each person enters this stage at a different rate of ketosis (since it happens in tandem with gluconeogenesis) depending on genetic factors, lifestyle indicators, as well as the previous history of fasting.

Stage 4 (Adapting to ketosis)

Once you have been in ketosis for several weeks, your body’s ketone-burning cells will have fully adapted to their new source of fuel. As a result of this, glucose is required less and less by the body. And as much as 50% of the body’s energy requirements can be met by ketones.

These are the four stages that your body will go through once you start to limit your carbohydrate intake, and continue to do so. Regardless of whether you are doing a ketogenic diet or are fasting from all food, you will go through all of the stages listed above.

The health benefits of ketosis

Ketosis has various health benefits resulting from the underlying change in energy production. Its therapeutic effects include, but are not limited to, its use in –

  1. Weight Loss — Recent studies have found that ketogenic diets (whose basis is ketosis) result in much more weight loss than traditional low-calorie and low-fat diets. (5, 6, 7). When fully adapted to ketosis, people also feel a lot less hungry (8, 9).
  2. Heart disease — In the process of achieving ketosis, one cuts down on carbs. This can result in lower blood triglycerides and total cholesterol, and higher HDL cholesterol (10).
  3. Acne — There is some evidence that ketosis may reduce the development of bacteria that cause acne as well as its recurrence (11).
  4. Cancer — Some studies indicate that ketosis may potentially contribute to cancer therapy by ensuring that cancer cells have no glucose to feed on. (12).
  5. Type-2 diabetes — Ketosis can potentially improve insulin sensitivity by up to 75%! (13).
  6. Epilepsy — Ketosis helps epileptic children who don’t respond to medication. As a result of this discovery, many children have benefitted massively regarding reductions in seizures. Some have also seen complete remission (14).

Ketosis Vs. Ketoacidosis

While ketosis is usually a part of metabolism, ketoacidosis is a dangerous metabolic condition that can be fatal if left untreated. In ketoacidosis, the bloodstream gets flooded with potentially threatening levels of glucose and ketones. As a result of this, blood becomes exceptionally acidic, which is a dangerous condition.

People sometimes think that ketosis and ketoacidosis are the same things. The truth, however, is that ketoacidosis is mostly found in people who have uncontrolled type 1 diabetes.

It has also been found in people with type 2 diabetes, although this is not as common an occurrence as in type 1 diabetes patients (15). It has also been seen in people who severely abused alcohol (16).

Side effects of ketosis

Possible side effects of ketosis include constipation, fatigue, headache, bad breath, and high cholesterol levels (17). Most of these symptoms occur within the first week of ketosis and are temporary.

They should ideally disappear in a few days, and in a couple of weeks, they go for sure. You can avoid most of these side effects by ensuring enough fluid and salt intake.

As an important note, however, people who are taking drugs which affect overall blood sugar levels should consult with a doctor before attempting to go on ketosis, as this may reduce the need for medication.

How to know if you are in ketosis?

There are various physical indications that your body will send you if you are in ketosis. Be on the lookout for these symptoms, as they are a sure shot sign of being in ketosis.

  1. More Frequent Urination — Due to increased production of acetoacetate, a ketone body, you will feel the need to go the bathroom more often.
  2. Dry Mouth — The increased urination results in having a dry mouth as well as increased thirst. It is advisable at this stage to drink plenty of water and salts, to make a quick recovery from this condition.
  3. Bad Breath — Acetone is the same chemical found in nail polish remover. You might experience temporary halitosis since this chemical is partially excreted in our breath. Others might describe the lousy smell as of overripe fruit. However, this condition is temporary and disappears in a week or so.
  4. Reduced Hunger and Increased Energy — This is an effect that you will only encounter once you have spent some time in ketosis, and when your body has fully adapted to this new technique of metabolism.

While these indicators will not give you an accurate reading of what your ketone levels are, you can rely on them to tell you whether or not you are in ketosis.

To get a more realistic understanding of where your ketone levels are, you can use urine strips, breath ketone analyzers, or blood ketone meters.


Over to on what is ketosis

Ketosis is a complex metabolic state which is achieved by substantially limiting one’s carbohydrate intake for a significant period.

To accomplish this, one has to go from glycolysis (glucose produces energy) to gluconeogenesis (stored glycogen produces energy) and ketogenesis (burning fat produces energy).

The healthiest and longest lasting method of achieving ketosis is through adhering strictly to a ketogenic diet. Other ways of reaching ketosis include extreme fasting and intense exercise regime.

But even if you achieve ketosis through this, it will be a lot harder to sustain since the process primarily depends on the food we consume.

Was this article helpful?
Thanks for letting us know!