Understanding the ketogenic diet - an introduction
Alicja Kowalska
2026-03-23
3 min. read
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Diets that limit or exclude certain nutrients are gaining more popularity year after year. The primary goal of these diets is usually weight reduction. However, is it enough to simply eliminate a particular nutrient from our daily diet to shed unwanted pounds?
Fundamentals of the ketogenic diet
The ketogenic diet is one of the most controversial methods of reducing diet, which aims to provide a minimal amount of calories from carbohydrates and meet the energy requirement from fats and proteins. Hunger was used as a therapeutic measure for epilepsy in the time of Hippocrates, but due to the risk of using it for too long, Dr. Russell Wilder and Dr. Rollin Woodyatt of the Mayo Clinic developed a ketogenic diet in the 1920s. Unlike traditional nutrition, where carbohydrates make up about 55-65%, protein 10-15%, and fat 25-30%, in the ketogenic diet, fats (about 80-90%) are the main source of energy, and carbohydrates and proteins make up the rest. In such a state, the body is without its main source of energy (carbohydrates), so it must rely on other sources of energy - fats (specifically, ketone bodies). In such conditions, ketosis occurs, a state similar to a fast. The early improvement in well-being that sets in is the result of the produced ketone bodies. The ketogenic diet can lead to deficiencies in vitamins and minerals, so supplementation is indicated, including calcium, zinc, B-complex vitamins, vitamins C, D, and omega-3 fatty acids.
High-fat diet – recommended and non-recommended products
A diet high in fat incorporates products that deliver substantial amounts of both saturated and unsaturated fats. Individuals adhering to a high-fat diet are advised to use cream that contains 36% fat instead of 12% fat. To induce a state of ketosis in the body, proponents of the high-fat diet recommend consuming certain products. Maintaining appropriate proportions between them is also crucial.
Recommended foodstuffs in the ketogenic diet:
sources of fats: plant-based oils, such as flaxseed, rapeseed, sunflower, coconut oil, mayonnaise, cream (with a higher concentration of fat, the better), butter, lard, avocado, walnuts, hazelnuts, kidney beans, almonds, pumpkin seeds, flax seeds, chia seeds, and olives; sources of protein: pork, beef, wild boar, lamb, chicken, fish, seafood, and eggs; sources of carbohydrates: fruits and vegetables should contain minimal amounts of carbohydrates, such as tomatoes, cucumbers, lettuce, spinach, cabbage, Brussels sprouts, eggplant, zucchini, broccoli; strawberries, blueberries, bilberries, raspberries, tangerines, grapefruits.
Not recommended products in the ketogenic diet:
– Cereal products – various grains, rice, pasta, bread, flour, cereal flakes; – Starchy vegetables – potatoes, carrots, beets; – Pulses – lentils, celery, peas and beans, – Fruits – bananas, grapes, pineapples, watermelons; – Sugar sources – sweets, cakes, confectionery, chocolate bars, chocolate, carbonated beverages, juices; – Alcohol.
The process of ketogenesis in the ketogenic diet
High fat consumption along with limited carbohydrate provision leads to the blockage of fatty acid oxidation, which results in the formation of ketone bodies such as acetone, acetooktane, and beta-hydroxymalanes. The formation of ketones leads to ketosis, which is common in people with diabetes mellitus. Ketone bodies do not form if appropriate amounts of carbohydrates are provided (responsible nutrition). The ketone body level can be checked through urine and/or blood tests. They most commonly appear when less than 50g of carbohydrates/day are provided or when <10% of daily kilocalories come from carbohydrate-containing products. To ensure proper functioning, glucose provision to brain tissue, renal cortex, and white and red blood cells is necessary. However, even these tissues can partially switch to another energy source during fasting – ketone bodies.
Keto diet – application and contraindications for use
In certain cases, the use of the keto diet is justified. However, in the case of neurodegenerative diseases such as drug-resistant epilepsy in children, congenital metabolic defects, Rett syndrome, Doose syndrome, Dravet syndrome, and Gaucher disease, it should be used under strict medical supervision and nutrition counseling. In cases of Alzheimer's disease, early Parkinson's disease, autism, and some types of epilepsy, the keto diet can be used as a supportive therapy. A meta-analysis of several clinical studies (X. Y. Liu et al., 2019) in more than 1000 children with drug-resistant epilepsy who were under observation for 3 or 6 months confirmed the effectiveness of the keto diet in reducing seizures. Investigations are being conducted into the effectiveness of the keto diet in the treatment of cancer, as it has been observed that low-carbohydrate diets play a role in reducing head and neck tumors. The KETOCOMP studies by R. J. Klement and R. A. Sweeney confirmed that the keto diet is effective as a supportive therapy in conjunction with standard treatment. A tumor regression was observed in 5 patients in the early stage of the disease. However, further studies with larger control groups are needed. The effect of the keto diet on the occurrence of migraine headaches is also being investigated. It is important to note that in the mentioned diseases, a doctor should always be consulted before introducing a specific diet. The keto diet should not be used by people with kidney, liver, thyroid, and pancreas diseases.
For example, the benefits of a ketogenic diet include:
– diminished feeling of hunger – increased fat input affects hormones (such as cholecystokinin) that weaken intestinal peristalsis (the movement of food content) and suppress hunger, – restriction of desire for food consumption – ketones produced by the body impact the nervous system (and specifically, the satiety center in the brain), – enhanced response of tissues to insulin, – decreased number of epileptic seizures.
Examples of deficiencies in the ketogenic diet:
Potential detrimental effects on the gut microbiota Reduction in the number of Bifidobacterium bacteria that protect the body from infection and inflammation, and increase in harmful Bacteroides bacteria, possible inflammation of the gut mucosa and hormonal imbalances, potential risk of cardiovascular diseases such as atherosclerosis, coronary heart disease, heart attack, or stroke (primarily due to saturated fatty acids and LDL cholesterol), potential deterioration of well-being and irritability, reduced tolerance to physical activity (decrease in neurotransmitter levels, such as serotonin, and loss of glycogen reserves). Each diet has its advantages and disadvantages, which should be taken into account before starting. It is also worth consulting with a doctor and a nutritionist whether introducing a particular diet is appropriate in a particular case. It should be emphasized that the application of elimination diets and adherence to their principles can be difficult. If the goal is weight loss, it is worth focusing on a balanced diet that takes into account an appropriate calorie deficit. When choosing a diet, it is not advisable to follow fads, but to make conscious decisions after consulting with an expert.
