The term 'ketogenic diet' (KD) is used to mean an isocaloric, high-fat, extremely low-carbohydrate diet. It is a possible form of treatment for seizures which cannot be stopped with medication and for the treatment of special metabolic disorders (e.g. for pyruvate dehydrogenase deficiency and for glucose transport defect). The mode of action of the KD is unknown. Ultimately, the reduced glycolysis leads to a considerable increase in activated acetic acid (acetyl-CoA), which results in a condensation of acetyl-CoA and the formation of ketone bodies, such as acetic acid, b-hydroxybutyric acid and acetone. It is thought that the related acidosis leads to changes in the fat status, in the water and salt balance and in the energy metabolism in the brain. It is possible that the ketone bodies themselves are also involved.
Use of these diets requires significant discipline with precise calculation of the meals and exact weighing of foods. Various metabolic disorders need to be ruled out before starting the diet.
The diet can be started with a two to five day starvation diet until the occurrence of massive ketonuria. This is followed by the gradual introduction of the KD. The energy supply should be isocaloric. It must be ensured that there is a sufficient supply of essential micronutrients (B vitamins, vitamin C, calcium, iron and zinc) and these must be supplemented in a targeted manner if necessary. A KD must never be stopped abruptly, because a supply of carbohydrates that is too rapid can trigger seizures, i.e. if it is intended that the diet will be stopped then it is advisable to slowly reduce the fat-carbohydrate-protein ratio in a controlled manner.
The best proven effectiveness of the KD is between the ages of two and five. It is possible to assess the success of the treatment in terms of seizure reduction after roughly four to eight weeks. If unsuccessful then the diet will be stopped again after a transition phase of a few days. Otherwise, this form of treatment can be carried out for several months up to around three years. After an initial scarce level of data, more recent studies are showing good levels of tolerance and effectiveness in adults. Comparative studies between classic KD and the one with MCT fats have shown no significant differences in effectiveness. The possible increase in the carbohydrate and protein content within the MCT fats diet has a favourable effect on compliance and acceptance of the diet.