OVERVIEW: WHAT IS THE KETOGENIC DIET?
The ketogenic diet is a high-fat, adequate-protein, low-carbohydrate diet that is carefully calculated by a dietitian and menus created for a parent to follow.1 A ketogenic diet ratio of 4:1 describes the ratio of grams of fat to both carbohydrate and protein combined, and provides 90% of calories from fat (Fig. 53–1). A 3:1 ratio is used primarily for infants and adolescents in whom either higher protein or more carbohydrates are needed for either growth or tolerability.
Daily calories provided on different diets. (A) Ketogenic diet. (B) Modified Atkins diet. (C) Standard diet.
Foods are carefully weighed and measured based on either dietitian-created meal plans or family-oriented computerized exchange program. In most cases, calories are restricted to 75% of daily requirements, although both increases and decreases from this may be made based on the individual child's daily metabolic demands to achieve an ideal body mass index.1 Fluids are also restricted to 85% of the daily allowance. Neither calorie nor fluid restriction has ever been demonstrated to be effective in children and many dietitians will target either 100% or the baseline prediet intake of each child.
The diet can be provided as solids, liquids (formula), or as a combination of both. Solid foods eaten not only include 36% heavy whipping cream, mayonnaise, oil, butter, cheese, hot dogs, and other high-fat foods but also protein sources typically totaling 1 g/kg body weight per day. The majority of the small amounts of remaining calories include carbohydrates such as fruits and vegetables, which help alleviate constipation. Many families have been very creative in recipe and meal choices (Fig. 53–2).
Typical meals provided on the ketogenic diet. Salad with walnuts (A), blueberry tart (B), sausage and cabbage dinner with heavy cream (C). (Photos courtesy Dr. Patti Vining.)
The diet can also be easily implemented as a formula, either using a single powdered source such as Nutricia KetoCal®, (Fig. 53–3) available in either a 4:1 or now 3:1 preparation, or "modular" components comprised of Ross Carbohydrate-Free® and Polycose® with Novartis Microlipid®.2 This liquid method of diet administration is used predominantly in infants and gastrostomy-tube fed children and compliance is assured. A formula-only diet has been demonstrated to be very effective, with approximately double the likelihood of a >90% seizure reduction compared to all children on the diet, possibly due to improved compliance.2,3
Nutricia KetoCal®. Powder (A), Liquid (B).