The ketogenic diet, a diet high in fat, moderate in protein and low in carbohydrates, shifts the body’s primary metabolic energy source from the use of glucose to the use of fat, which is metabolized by the liver to produce ketone bodies, resulting in a series of responses in the body. This method of treating disease with a dietary formula containing a high percentage of fat and a low percentage of protein and carbohydrates that mimics the body’s response to starvation by producing ketone bodies through lipolytic metabolism is called ketogenic diet therapy. The ketogenic diet was first developed to simulate a state of ketosis from starvation and is used primarily for the treatment of refractory epilepsy, especially in children, and also for the treatment of mitochondrial disorders, among others. In recent years it has been used for the treatment of childhood solitary disorders with the most promising results. The ketogenic ratio is the ratio of fat/carbohydrate + protein, and this ratio is the weight ratio. 1. Mechanism of action of ketogenic diet During feeding, glucose enters the brain by promoting glucose transport carriers, and during fasting, fatty acids provide energy for muscles and other tissues, while ketone bodies produced by fatty acids and ketogenic amino acids in the liver can enter the brain to provide another kind of energy through transport carriers, which can produce an anticonvulsant effect on the brain. In addition, the ketogenic diet alters the body’s energy metabolism and improves intracellular mitochondrial function, which in turn can be helpful in many neurological disorders of the brain. Ketone bodies, a hallmark of the ketogenic diet, are the result of a buildup of metabolic intermediates resulting from incomplete fat burning. Ketone bodies have a sedative and appetite suppressant effect. Some popular diet recipes marked by calories and low carbohydrates also produce a state of ketosis. The appetite suppressing effect of ketone bodies can explain why these diets can be accepted by dieters without feeling too hungry, and ketone bodies also have an anticonvulsant effect Ketogenic diets have been studied in many fields for a long time. Individual case reports have also appeared in China. 2. Clinical application of ketogenic diet in the treatment of autism in children A pilot trial study of ketogenic diet in autistic behavior in children was conducted with 30 children aged between four and ten years old. The ketogenic diet was conducted for six months, with four weeks of continuous ketogenesis and two weeks of intervals. According to the Childhood Autism Rating Scale, improvements in several parameters were recorded. The ketogenic diet can be used for autistic behavior as an additional or alternative therapy. 3. Adverse effects of the ketogenic diet (1) Short-term possible problems Hunger and thirst: Patients will obviously feel hungry and want to eat due to fasting or at the beginning of the ketogenic diet. Parents should give a small amount of sugar-free food, take the patient away from the eating environment, take distractions such as playing games and telling stories, etc. A small amount of vegetables can be given or moderate amounts of water can be drunk to relieve the problem in the 2-4 weeks after the start. Gastrointestinal symptoms: Patients may have gastrointestinal symptoms such as nausea, vomiting and diarrhea, mainly due to intestinal spasms caused by medium chain fats. Parents can give oral elimination scopolamine tablets to relieve the symptoms under the guidance of the doctor or nurse. Food refusal: Since ketogenic diets often start with powder or emulsion finished products, some emulsion finished products with a single taste may refuse to eat after a few days, which requires parental encouragement and additional food flavors. The ketogenic nutritional powder of the Ketogenic series is equipped with a variety of different flavors of sugar-free flavoring – ketogenic partner, which largely solves the problem of food refusal caused by a single taste. (2) Possible long-term problems Constipation: Constipation is mainly caused by small amounts of food, low fiber content, reduced fluid intake and high fat concentration in the diet. Constipation occurs when the excreted stool is hard, like a small ball, and sometimes difficult to defecate. Constipation, which can cause abdominal pain and discomfort, can be largely resolved by ensuring that the patient consumes the proper amount of fluids and sugar-free dietary fiber each day. If the constipation does not improve with the above methods, laxatives, stool softeners or enemas can be used under medical supervision. Hyperlipidemia: This diet-induced increase in blood lipids does not affect the patient. If abnormalities occur, the patient can lower the ketogenic diet ratio and increase the ratio of polyunsaturated fatty acids. If the lipids remain elevated and there is no other clear identifiable cause, the physician may recommend screening the parents’ lipids to investigate whether there is a genetic link. Growth Disorders: Patients on a ketogenic diet who are young grow more slowly than normal children, but they are usually normal in height growth. Regular height and weight measurements are taken to determine bone age against the normal child height and weight growth tables. To avoid problems with growth disturbances, patients can consume appropriate protein, vitamins and minerals, especially calcium, and reduce the proportion of ketogenic diet if necessary.