High-fat, adequate-protein, low-carbohydrate diet
The ketogenic diet is a high-fat, adequate-protein, low-carbohydrate diet that in medicine is used primarily to treat difficult-to-control (refractory) epilepsy in children. The diet forces the body to burn fats rather than carbohydrates. This classic ketogenic diet contains a 4:1 ratio by weight of fat to combined protein and carbohydrate. A variant of the classic diet known as the MCT ketogenic diet uses a form of coconut oil, which is rich in MCTs, to provide around half the calories. When drugs fail, other options include epilepsy surgery, vagus nerve stimulation, and the ketogenic diet.
Physicians of ancient Greece treated diseases, including epilepsy, by altering their patients' diet. His trial on a few epilepsy patients in 1921 was the first use of the ketogenic diet as a treatment for epilepsy. The diet proved to be very successful in children: Peterman reported in 1925 that 95% of 37 young patients had improved seizure control on the diet and 60% became seizure-free. Barborka concluded that adults were least likely to benefit from the diet, and the use of the ketogenic diet in adults was not studied again until 1999.
The severe carbohydrate restrictions of the classic ketogenic diet made it difficult for parents to produce palatable meals that their children would tolerate. Most children improved in both seizure control and alertness, results that were similar to the classic ketogenic diet. The MCT diet replaced the classic ketogenic diet in many hospitals, though some devised diets that were a combination of the two.
There followed an explosion of scientific interest in the diet. Children with refractory epilepsy are more likely to benefit from the ketogenic diet than from trying another anticonvulsant drug. Another difference between older and newer studies is that the type of patients treated with the ketogenic diet has changed over time. In the largest trial of the ketogenic diet with a non-diet control, nearly 38% of the children and young people had half or fewer seizures with the diet compared 6% with the group not assigned to the diet. A systematic review in 2018 looked at 16 studies on the ketogenic diet in adults. The ketogenic diet is indicated as an adjunctive (additional) treatment in children and young people with drug-resistant epilepsy. About a third of epilepsy centres that offer the ketogenic diet also offer a dietary therapy to adults. The ketogenic diet is usually initiated in combination with the patient's existing anticonvulsant regimen, though patients may be weaned off anticonvulsants if the diet is successful. Like many anticonvulsant drugs, the ketogenic diet has an adverse effect on bone health. The ketogenic diet is a medical nutrition therapy that involves participants from various disciplines. Some people terminate the diet or switch to a less demanding diet, like the modified Atkins diet or the low-glycaemic index treatment diet, because they find the difficulties too great.
The Johns Hopkins Hospital protocol for initiating the ketogenic diet has been widely adopted. Because of the risk of complications during ketogenic diet initiation, most centres begin the diet under close medical supervision in the hospital. The diet may be modified if seizure frequency remains high, or the child is losing weight. The total diet duration is up to the treating ketogenic diet team and parents; durations up to 12 years have been studied and found beneficial. Children who discontinue the diet after achieving seizure freedom have about a 20% risk of seizures returning. Such children may remain on the diet longer than average, and children with tuberous sclerosis who achieve seizure freedom could remain on the ketogenic diet indefinitely.
The ketogenic diet is calculated by a dietitian for each child. The ketogenic ratio of the diet compares the weight of fat to the combined weight of carbohydrate and protein. The classic ketogenic diet is not a balanced diet and only contains tiny portions of fresh fruit and vegetables, fortified cereals, and calcium-rich foods. The ketogenic diet team at Johns Hopkins Hospital modified the Atkins diet by removing the aim of achieving weight loss, extending the induction phase indefinitely, and specifically encouraging fat consumption. Although it is also a high-fat diet (with approximately 60% calories from fat), the LGIT allows more carbohydrate than either the classic ketogenic diet or the modified Atkins diet, approximately 40–60 g per day. Infants and patients fed via a gastrostomy tube can also be given a ketogenic diet. It is used to administer the 4:1 ratio classic ketogenic diet in children over one year. The Indian ketogenic diet is started without a fast due to cultural opposition towards fasting in children. The low-fat, high-carbohydrate nature of the normal Indian and Asian diet means that their ketogenic diets typically have a lower ketogenic ratio (1:1) than in America and Europe. The ketogenic diet has been studied in at least 14 rodent animal models of seizures. The ketogenic diet has been found to have antiepileptogenic properties in rats.
A 2018 review looked at the evidence from preclinical and clinical studies of ketogenic diets in cancer therapy.
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