Ketogenic diet

Did You Know?

• Epilepsy affects around 50 million people worldwide and is one of the most common neurological disorders after migraine and stroke.
• The ketogenic diet is approved by national clinical guidelines in Scotland, England, and Wales and is reimbursed by nearly all US insurance companies.

History

The ketogenic diet was developed to reproduce the success of fasting in treating epilepsy while removing its limitations. Although popular in the 1920s and 1930s, it was largely abandoned after effective anticonvulsant drugs appeared. Today, about 25–30% of individuals with epilepsy fail to control seizures with medication, and for this group—especially children—the diet has regained a role. Erasistratus recommended fasting, and Galen believed an attenuating diet could help. The first modern study of fasting for epilepsy was conducted in France in 1911, involving twenty patients who underwent a low-calorie vegetarian diet combined with fasting and purging; two benefited greatly, but most could not maintain compliance. Unlike the medication potassium bromide, which dulled the mind, the diet improved patients' mental capabilities.

Efficacy

The ketogenic diet can cut seizure frequency by more than half for about half of those who try it, and by over 90% for a third of patients. Among children who respond, three-quarters show improvement within two weeks, though experts advise trying the diet for at least three months before concluding it doesn’t work. For children with hard-to-control epilepsy, the diet is more likely to help than another anticonvulsant drug. Adolescents and adults may also see benefits, but sticking with the oral diet is often difficult. Early research, such as a 1925 study, reported impressive results: 60% of patients became seizure-free and another 35% saw a 50% reduction. However, those older studies had selection bias, since they excluded patients who couldn’t start or maintain the diet. Modern studies address this by using prospective cohorts and intent-to-treat analysis, which includes all patients regardless of whether they completed the treatment. The patient population has also shifted; today’s children have typically already failed several anticonvulsant drugs, meaning their epilepsy is more severe. Treatment protocols have changed too. Older methods began with a prolonged fast and fluid restriction, but fluid restriction is now avoided because it raises the risk of constipation and kidney stones.

Implementation

The ketogenic diet is a medical nutrition therapy involving a multidisciplinary team: a registered paediatric dietitian, a paediatric neurologist experienced in the diet, a registered nurse familiar with childhood epilepsy, and possibly a medical social worker and pharmacist. Caregivers must be educated in many aspects of the diet for safe implementation. The time commitment for measuring and planning meals can be challenging, and any unplanned eating may break the nutritional balance. Some people switch to less demanding diets such as the modified Atkins diet or low-glycaemic index treatment. The Johns Hopkins Hospital protocol, widely adopted, begins with a consultation and a short hospital admission. Patients are screened for contraindications, and dietary parameters are selected: ketogenic ratio, calorie requirements, and fluid intake. The day before admission, carbohydrate intake is reduced and the patient fasts after the evening meal. On admission, only calorie- and caffeine-free fluids are allowed until a restricted-calorie dinner. Over subsequent days, calorie intake increases, and by the fourth day the patient is discharged after a ketogenic breakfast. Where possible, medications are changed to carbohydrate-free formulations.

Variants

The ketogenic diet is calculated individually for each child, considering age, weight, activity level, culture, and food preferences. Energy requirements are set at 80–90% of the recommended daily amounts for the child's age, as the high-fat diet requires less energy to process. The ketogenic ratio is typically 4:1, but children under 18 months, over 12 years, or who are obese may start at 3:1. Fat provides 9 kcal/g, while carbohydrate and protein provide 4 kcal/g, so portions are smaller than normal. Protein is set at about 1 g per kg of body weight to allow for growth. Carbohydrate allowance is determined by what remains while maintaining the chosen ratio, and any carbohydrates in medications or supplements must be subtracted. The total daily amounts are divided evenly across meals. A variant called the MCT ketogenic diet uses coconut oil rich in medium-chain triglycerides, which are more ketogenic, allowing a greater proportion of carbohydrate and protein and more food variety.