 The ketogenic diet is calculated by a dietitian for each child . Age , weight , activity levels , culture and food preferences all affect the meal plan . First , the energy requirements are set at 80 – 90 % of the recommended daily amounts ( RDA ) for the child 's age ( the high @-@ fat diet requires less energy to process than a typical high @-@ carbohydrate diet ) . Highly active children or those with muscle spasticity require more calories than this ; immobile children require less . The ketogenic ratio of the diet compares the weight of fat to the combined weight of carbohydrate and protein . This is typically 4 : 1 , but children who are younger than 18 months , older than 12 years , or who are obese may be started on a 3 : 1 ratio . Fat is energy @-@ rich , with 9 kcal / g ( 38 kJ / g ) compared to 4 kcal / g ( 17 kJ / g ) for carbohydrate or protein , so portions on the ketogenic diet are smaller than normal . The quantity of fat in the diet can be calculated from the overall energy requirements and the chosen ketogenic ratio . Next , the protein levels are set to allow for growth and body maintenance , and are around 1 g protein for each kg of body weight . Lastly , the amount of carbohydrate is set according to what allowance is left while maintaining the chosen ratio . Any carbohydrate in medications or supplements must be subtracted from this allowance . The total daily amount of fat , protein and carbohydrate is then evenly divided across the meals . 
