What Is Ketosis?

The application of a state of ketosis could be beneficial for many people in terms of preventing complex pathologies or improving their management.
What Is Ketosis?
Saúl Sánchez

Written and verified by el nutricionista Saúl Sánchez in 27 March, 2021.

Last update: 27 March, 2021

Ketosis is a metabolic condition that occurs when there’s a low availability of a specific nutrient. It’s the key mechanism in the ketogenic diet and can have positive health consequences if applied correctly. In this article, we’ll tell you everything there is to know about this process.

Before we begin, it should be noted that ketogenic diets have been the subject of much scientific discussion. This disagreement continues to this day, although it is true that more and more evidence is being collected in favor of its use in certain contexts.

Mechanism of ketosis

The liver participates in the state of ketosis.
The liver is a fundamental organ from a metabolic point of view. The production of ketone bodies occurs there.

When there isn’t a sufficient amount of carbohydrates in the diet, the body has to resort to other ways of producing them in the liver. This is what is known as ketogenesis.

Fatty acids and amino acids are transformed into glucose through a process called gluconeogenesis, in turn producing a series of by-products called ketone bodies. These elements can also be used for energy production.

In fact, ketone bodies are one of the brain’s favorite fuels, according to research published in the International Journal of Molecular Sciences .

It should be noted that this mechanism takes place because glucose is the energy substrate of the body’s cells. Most metabolic reactions require this molecule to function, and because of this, a certain concentration is necessary for the body.

If it isn’t administered through diet, it has to be produced endogenously. Fortunately, the mechanism that handles this task is very efficient.

Consequences of ketosis

The ketosis process in the body creates a series of consequences and adaptations at a physiological level. Although they used to be considered harmful, science has changed its position on the matter.

Thus, the use of ketone bodies as brain fuel is associated with a lower risk of developing neurodegenerative pathologies, as stated in a study published in the International Journal of Molecular Sciences.

The state of ketosis is associated with a lower production of beta-amyloid compounds, linked to the risk of developing problems such as Parkinson’s or Alzheimer’s.

There is also strong evidence to date about the protection that ketosis provides against epilepsy. Thus, keeping the carbohydrate intake in the diet limited is able to reduce seizures by more than 50% in a large number of individuals, even when medication isn’t effective.

Ketosis and cancer

One of the aspects that causes the most interest in this area is the relationship between the state of ketosis and the reduction of tumor evolution. Experts are currently conducting considerable research into this mechanism, and it could represent a turning point when it comes to cancer treatment.

The first thing to be clear about here is that tumor cells use glucose as their main fuel. From here on, access to this molecule by the rest of the cells of the body is restricted.

The state of ketosis could delay or block tumor reproduction, since these masses are unable to use ketone bodies as an energy substrate.

What do the studies say?

According to research published in the journal Molecular Metabolism, applying a ketogenic diet could be effective in enhancing the effects of chemotherapy, thus increasing the survival rate against various types of cancer.

However, it should be noted that the results are more satisfactory in glucose-dependent tumors. These are the colon, breast, head or neck, and lung.

Even so, the application of the ketogenic diet in these contexts has certain limitations today. It may represent a breakthrough in the treatment of the tumor, but there’s still much to discover about this process. Most of the studies carried out have small samples.

Ketosis and metabolic pathology

Another application context for ketogenic diets and the state of ketosis is that of diabetic patients. However, certain precautions must be taken in this regard.

In general, a balanced distribution of carbohydrates in the diet is recommended for the treatment of diabetes. It’s strange how an illness that causes a wrong handling of these nutrients is being cured, or at least helped, by increasing its presence in the diet.

As expected, the response to treatment wasn’t usually very good. In few cases did they manage to stop the disease from progressing, and ended up resorting to drugs to control it.

What do the most recent studies say?

Researchers have found that restricting carbohydrates in the diet, and implementing a state of ketosis, could be effective in managing diabetes.

This is concluded by an investigation published in the journal Nutrition & Diabetes, where an improvement in metabolic pathology and in the state of body composition is found from the ketogenic diet.

Despite the findings, it should be noted that certain precautions must be taken in the implementation of these models.

In subjects with type 2 diabetes, it isn’t very dangerous, but in those with type 1 diabetes, a certain control over glycemia must be started. Whatever the case, professional advice is always necessary.

Neither should we forget that the application of the state of ketosis in people with a metabolic pathology or obesity usually creates an improvement in the state of body composition. In this way, it’s possible to increase the oxidation of fats, thus reducing their deposits in the body.

Ketosis status, protein intake, and health

One of the main controversies when it comes to maintaining a state of ketosis is whether high protein intake can be harmful to health.

The most current studies, such as the one published in the journal Food & Function, affirm that it’s possible to increase said intake up to 2 g / kg of weight/day without negative consequences.

The hypotheses of possible kidney and liver damage derived from a high protein intake seem to be ruled out today. Despite this, you need to be careful with protein intake in situations of already established chronic kidney disease or failure.

With these findings, one of the most important walls when proposing a state of ketosis is demolished. It can be said that it has positive effects on health, and that the possible negative consequences are very limited.

Even within the idea that fat intake puts the functioning of the cardiovascular system at risk, much progress has been made. Although it was claimed in the past that dietary cholesterol and saturated fat could pose a problem for heart health, this relationship is currently denied.

Conditions to induce ketosis

When looking for a state of ketosis, it’s important to respect the limitation of 50 grams (2 oz) per day of carbohydrates in the diet. These must be distributed throughout the day, so as not to cause peaks in blood glucose that break the metabolic situation.

Even the strictest ketogenic diets go for a maximum intake of 20 grams (0.8 oz) of sugar throughout the day. In these cases, the intake of fruits is highly compromised, which could be negative for health in the medium term.

The best way is to always propose the most flexible protocol possible, thus ensuring a certain variety in the diet. This is one of the pillars of a healthy diet.

Variations in protein intake can also be experienced. Although the classic ketogenic diets advocated a consumption of 0.8 g / kg weight/day, currently experts are recommending increasing protein intake until reaching 20-25% of the recommended daily energy through this nutrient.

It should also be noted how important it is to ensure that the fatty acids consumed are of high quality. In order to do this, you need to avoid subjecting them to high temperatures, as this causes a change in their spatial configuration, creating trans fats that are harmful to the body.

Side effects of ketosis

Ketosis can cause abdominal pain.
Some nonspecific gastrointestinal disorders can occur upon reaching a state of ketosis.

While ketosis and ketogenic diets are considered safe in the long term, it’s true that in the short term they can cause a number of side effects. These are usually of a gastrointestinal character and not everyone tolerates them in the same way.

We’re talking here about nausea, dizziness, weakness, and constipation, especially during the first days of applying this kind of diet. However, as the body gets used to using ketones for fuel, these problems go away.

Despite everything, for some people, this condition is a great handicap and discomfort. It negatively conditions adherence to this type of diet and makes it impossible to put it into practice.

Ketosis, a metabolic state that can be healthy

As we have noted, ketosis isn’t suited to everyone. Many people don’t develop good adherence to ketogenic diets, which conditions their application. However, if put into practice, it’s quite possible to experience benefits from them.

Although until a few years ago they were only used in patients with medication-insensitive epilepsy, today their application framework has expanded. Thus, the possibility of using them in cases of cancer patients, metabolic problems, or even in healthy people is well worth considering.



  • Jensen NJ, Wodschow HZ, Nilsson M, Rungby J. Effects of Ketone Bodies on Brain Metabolism and Function in Neurodegenerative Diseases. Int J Mol Sci. 2020 Nov 20;21(22):8767. doi: 10.3390/ijms21228767. PMID: 33233502; PMCID: PMC7699472.
  • Rusek M, Pluta R, Ułamek-Kozioł M, Czuczwar SJ. Ketogenic Diet in Alzheimer’s Disease. Int J Mol Sci. 2019 Aug 9;20(16):3892. doi: 10.3390/ijms20163892. PMID: 31405021; PMCID: PMC6720297.
  • Sampaio LP. Ketogenic diet for epilepsy treatment. Arq Neuropsiquiatr. 2016 Oct;74(10):842-848. doi: 10.1590/0004-282X20160116. PMID: 27759811.
  • Weber DD, Aminzadeh-Gohari S, Tulipan J, Catalano L, Feichtinger RG, Kofler B. Ketogenic diet in the treatment of cancer – Where do we stand? Mol Metab. 2020 Mar;33:102-121. doi: 10.1016/j.molmet.2019.06.026. Epub 2019 Jul 27. PMID: 31399389; PMCID: PMC7056920.
  • Wu G. Dietary protein intake and human health. Food Funct. 2016 Mar;7(3):1251-65. doi: 10.1039/c5fo01530h. PMID: 26797090.
  • Goday A, Bellido D, Sajoux I, Crujeiras AB, Burguera B, García-Luna PP, Oleaga A, Moreno B, Casanueva FF. Short-term safety, tolerability and efficacy of a very low-calorie-ketogenic diet interventional weight loss program versus hypocaloric diet in patients with type 2 diabetes mellitus. Nutr Diabetes. 2016 Sep 19;6(9):e230. doi: 10.1038/nutd.2016.36. PMID: 27643725; PMCID: PMC5048014.