Introduction
The ketogenic diet has long been much more than just a short-lived nutrition trend. Originally developed as a therapy against epilepsy, it is today applied in many areas – from losing weight to the treatment of chronic diseases to competitive sport. But what is really behind it? Is this form of nutrition a scientifically founded concept or just another passing fad?
In this article you will learn everything about the history, the scientific basics, possible advantages, risks and the practical implementation of the ketogenic diet.
1. The history of the ketogenic diet
The idea of influencing the metabolism through a targeted way of eating is by no means new. Already in antiquity, fasting was used to treat illnesses. The modern term of the ketogenic diet emerged in the 1920s, when doctors found that a low-carbohydrate, high-fat diet could alleviate or even help reverse epileptic seizures in children.
Since then the concept has evolved and is today used successfully not only for epilepsy, but also for various chronic diseases, including:
- Metabolic diseases: type 2 diabetes, insulin resistance
- Cardiovascular diseases: high blood pressure, arteriosclerosis
- Neurodegenerative diseases: Alzheimer's, Parkinson's
- Autoimmune diseases: multiple sclerosis, Crohn's disease
- Psychiatric disorders: depression, bipolar disorder
- Various cancer diseases
Especially in recent years, the ketogenic diet is also gaining popularity in the sports field, as it is said to promote metabolic flexibility and enable efficient energy provision. In addition, the ketogenic diet is a popular method for weight reduction.
2. What happens in the body? The basics of ketosis
The ketogenic diet is based on a simple principle: When the body receives hardly any carbohydrates, it switches to fat burning and produces so-called ketone bodies.
Metabolic flexibility
A healthy body can switch between different energy sources: glucose (from carbohydrates) and ketone bodies (from fat). With a carbohydrate-rich diet, the body relies almost exclusively on glucose. In ketosis, by contrast, it preferentially uses fat as an energy source.
The most important ketone bodies
During ketosis the liver produces three main ketone bodies:
- Beta-hydroxybutyrate (BHB): main energy source for brain and muscles
- Acetoacetate: precursor of BHB, is also used as an energy source
- Acetone: by-product that is excreted via the breath (leads to typical “keto breath”)
Ketosis as a natural process - How is ketosis reached?
Ketosis is not an artificial state – it occurs in many life situations and can be reached in several ways:
- In infants who are fed with breast milk
- During prolonged fasting (from about 12–16 hours)
- Through intense physical activity, Training or cold exposure
- Through a high-fat or ketogenic diet
- Under certain circumstances, during prolonged darkness
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3. What is the ketogenic diet?
The classic ketogenic diet is characterised by a strict macronutrient distribution:
- 70–80 % of the calories from fat
- 20–25 % of the calories from protein
- 5–10 % of the calories from carbohydrates
With this way of eating, the main calories come from high-fat foods such as butter, oils, fatty fish, meat, eggs, avocados and nuts. Starchy foods, sugar, bread, pasta, rice and sweet fruits are excluded or very strongly reduced. However, starchy foods with a low glycaemic index, such as beetroot or carrots, can and should mostly still be consumed raw in moderation – as long as one stays within the prescribed macronutrient distribution. Low-starch vegetables such as all kinds of green leafy salads and vegetables, broccoli, cauliflower or cabbage are, by contrast, eaten without hesitation, as are fruits such as raspberries, etc.
On the plate, the food distribution often appears less fat-focused, since 1 gram of fat provides more than twice as many calories as protein or carbohydrates. As a result, the actual quantity ratio of the foods appears less extreme than the calculated macronutrient distribution. Even with a ketogenic diet, vegetables and salad can continue to make up the base and the largest part of the plate.
Many people who practise the ketogenic diet report positive changes in their well-being. Studies and reports of experience show, among other things, improved ability to concentrate and cognitive performance, less brain fog, a more stable energy level without feelings of tiredness or weakness and higher physical performance, less hunger, weight reduction, the reduction or regression of various pains, deeper sleep and an improved mood. These effects could be attributed, among other things, to the more stable blood sugar level (and general blood values), the reduction of inflammations and the ketone-based energy supply of the brain.
Sample daily plan for a classic ketogenic diet
A classic daily plan for a ketogenic diet could look like this:
- Breakfast: scrambled eggs with avocado and salmon
- Lunch: vegetables and salad with olive oil, cheese and nuts
- Dinner: grilled meat with broccoli and butter
- Snacks: almonds, macadamia nuts
Alternatively, the ketogenic diet can also be implemented with only two meals per day, which allows it to be combined optimally with intermittent fasting (e.g. 16:8). Breakfast or dinner is then skipped, and the calorie intake concentrates on two larger, filling meals. This combination can further optimise fat metabolism, ensure more stable energy levels and at the same time support the benefits of fasting.
Further forms of the ketogenic diet
Besides the classic ketogenic diet, there are also countless variations, used depending on the goal and individual tolerance:
- Modified Atkins diet: less strict, somewhat more protein and carbohydrates allowed
- Cyclical ketogenic diet: alternating ketogenic and more carbohydrate-rich days, weeks or months
Looked at somewhat more broadly, the ketogenic diet can be designed both vegetarian or even vegan (although this is considerably more difficult) – with plant-based fats such as avocados, olive and coconut oil and nuts – as well as go in a purely carnivorous direction, in which almost exclusively animal products are consumed. Ultimately, what is decisive in this context is that the form of nutrition leads to ketosis.
4. Saturated fatty acids: healthy or not?
Fat is not the same as fat. While unsaturated fatty acids (e.g. from avocados, nuts, olive oil) are considered healthy, saturated fatty acids (e.g. from butter, meat, cheese) are controversial.
For a long time, saturated fats were held responsible for cardiovascular diseases. Newer studies show, however, that perhaps it is not the saturated fat that is harmful, but rather that industrially hydrogenated fats (trans fats), processed carbohydrates and sugar play a larger role in the development of chronic diseases.
At the same time, there are indications that saturated fatty acids do not act the same way in all people. Thus, for example, the APO E4 gene could play a role: people who carry this genetic variant seem to possibly metabolise saturated fatty acids less well, which can lead to increased inflammation values. In such cases, a reduction of saturated fats could be sensible.
Equally complex and individual is the debate around LDL cholesterol. With a ketogenic diet, different reactions show up here: in some people the LDL values rise, while in others they remain stable or even decrease – presumably likewise due to genetic differences. However, it is increasingly assumed that an elevated LDL level alone is not decisive for cardiovascular health. Rather, further factors such as the density and size of the LDL particles play a decisive role: small, dense LDL particles are considered more problematic, while large, fluffy LDL particles are possibly less harmful.
These differences show that there is no universal rule for saturated fatty acids and cholesterol – individual genetic factors could play a decisive role.
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5. Does the human being need carbohydrates? The role of gluconeogenesis
A frequent argument against the ketogenic diet is that the brain needs glucose and that it is also decisive for our physical performance. In reality, however, the body can produce glucose (precisely because it is so important) from other sources – through so-called gluconeogenesis.
The liver can convert proteins and fats into glucose, so that even with a ketogenic diet, a low-carb diet or in case of famine, no deficiency arises. This means that carbohydrates (as has long been known from biochemistry) are not essential for the human being – but certain fats and amino acids are.
6. Measuring ketosis: various methods
Thanks to modern technology, ketosis can now be easily checked:
- Blood tests: measure beta-hydroxybutyrate (BHB) in the blood
- Breath tests: detect acetone in the breath
- Urine tests: simplest and cheapest method, but not always reliable
- Continuous ketone monitors: similar to CGMs for blood sugar
7. Side effects and implementation difficulties
The switch to the ketogenic diet can be challenging at first. Some people report side effects such as:
- Keto flu: tiredness, headaches, dizziness – often due to electrolyte deficiency
- Digestive problems: especially when not enough fibre is taken in
- Strong weight loss: can be problematic with too rapid a transition and insufficient food intake
These symptoms are, however, mostly connected with errors in the implementation, such as too few electrolytes, wrong macronutrient distribution, too little water or too abrupt a transition. A factor not to be underestimated is the social component, which can make the implementation of the ketogenic diet more difficult.
The ketogenic diet brings some challenges with it and can contain hidden pitfalls, which often lead to the mentioned errors in implementation. To avoid this, it is sensible to engage intensively with this form of nutrition beforehand – whether through sound specialist literature or with the support of a professional.
8. Contraindications
The ketogenic diet is not suitable for everyone. People with certain metabolic disorders, which are however rather rare, should avoid it or seek medical advice. These include:
- disorders of fatty acid breakdown, ketogenesis or ketolysis
- impairments of gluconeogenesis
- hyperinsulinism
In such cases, a ketogenic diet can carry health risks, since the body, due to missing enzymes etc., is not able to produce or utilise ketones efficiently.
Conclusion – miracle cure or waste of time?
The ketogenic diet in the classic sense can have great advantages for many people, but for others it may not be the optimal solution and can even be unsuitable in the case of certain disorders, such as the mentioned contraindications.
One possible reason for the different reactions could lie in genetic differences: depending on origin, it is possible that people metabolise fat, protein or carbohydrates differently well, depending on the diet of their ancestors over millennia.
At the same time, one should not make the mistake of tarring all carbohydrates with the same brush and making them blanketly responsible for the development of chronic diseases – similarly to what presumably happened for a long time with fats. It is important to differentiate: natural carbohydrates from regional and seasonal vegetables or unprocessed grain affect the body differently than heavily processed carbohydrates such as sugar or refined flours, which one also consumes daily all year round without taking the seasons into account. In addition, here too genetic differences play a role – what works well for one person does not necessarily have to be ideal for another.
In the end, there is probably no universal way of eating for all human beings. The ketogenic diet is an exciting concept – but its effect depends strongly on individual factors. Whoever considers a ketogenic diet should inform themselves well in advance or seek professional advice, in order to ensure a healthy and sustainable implementation.
