Abstracts

RATIONALE: The ketogenic diet (KD) comprises three main components: Restricted calories, High proportion of fat, and Fluid restriction. Lack of efficacy often is attributed to excessive caloric consumption as indicated by excessive weight gain (though other factors can also cause decreased efficacy, like noncompliance, excess fluids, unrecognized carbohydrate. Calories prescribed at initiation of KD are calculated based on recommended daily allowance (RDA) for age and weight. However, caloric needs can be measured using oxygen consumption and carbon dioxide production (indirect calorimetry). Accurate measurement of caloric need at diet onset is likely to prevent excess weight gain (or loss) during KD therapy.
METHODS: 21 patients (8 months - 69 years) who were able to complete indirect calorimetry were started on the KD. 20 had intractable epilepsy. One (69 years) had a dementing illness, polyglycosan body disease. Average age was 9.1 years. Initial calorie requirement was calculated based on RDA for age and weight. Indirect calorimetry was performed using a commercial device to measure oxygen consumption and carbon dioxide production. The calories prescribed at KD initiation were based on the results of calorimetry.
RESULTS: The caloric needs based on RDA ranged from 20 to 57 kcal/kg (average 46). The caloric needs calculated from calorimetry ranged from 22 to 101 (average 53). Seven of the 21patients had a difference between the measured and RDA estimated calorie requirement [gte] 25%. Three of 7 had calorimetry based values less than RDA values. Six of these 7 patients maintained weight within 300 gm at first follow up visit (22-163 days). Across the entire group of 21 patients, the average weight change was -200 gm ([plusminus]1.3 kg). For 13 patients (at first follow up), urine ketones were reported as usually [dsquote]large.[dsquote] For 5, ketones were consistently in the [dsquote]moderate-to-large[dsquote] range.
CONCLUSIONS: Indirect calorimetry testing to measure each individual[ssquote]s calorie requirements allowed adjustment of the KD prescription at diet initiation instead of at follow up. 33% of patients started on the KD had calorimetry based calorie requirements substantially ([plusminus]25%) different from RDA based values. For most of these patients, weight was stable between diet initiation and first follow up. Accurate prescription of the daily calorie requirement at initiation of KD usually results in stable weight at follow up. When patient weight is stable between visits, it eliminates a variable to which either lack of KD antiseizure efficacy or adverse effects might be attributed.
Objective: After reviewing this presentation, participants should be able to discuss accurate calculation of calorie requirements for the KD.