Epilepsy is one of a common neurological disorder. Antiepileptic drugs (AEDs) are usually the primary treatment of epilepsy. However, almost 30% of patients do not respond to AEDs and other treatments including ketogenic diet (KD) are used. The Ketogenic Diet (KD) is a low-carbohydrate, high fat, adequate-protein diet. In this study, investigators are going to compare two kinds of the ketogenic diet namely classical ketogenic diet and modified Atkins diet. Fifty children and adolescents with intractable epilepsy will be included, 25 patients in each group, and will receive the diet for three months on non-randomised basis. In the classical ketogenic diet, the diet with a ratio of 4 to 1 (4:1), each 4 grams of fat to each gram of carbohydrate plus protein, will be introduced. Classical ketogenic diet will be established on outpatient setting, without fasting and gradually. The modified Atkins diet will be applied by the ratio of 1:1 or 2:1, each 1 or 2 grams of fat to each gram of carbohydrate plus protein.

Inclusion Criteria:

• Children and adolescents age 1 to 18 years Have not responded well to at least two primary and one secondary antiepileptic drugs Have not received ketogenic diet therapy previously Absence of renal diseases history Absence of cardiovascular diseases history Absence of thyroid function disorders history Absence of cholesterol level more than 300 mg/dl and Triglyceride level more than 200 mg/dl Absence of inherited metabolic disorders that are contraindicated for ketogenic diet therapy including fatty acid oxidation disorders

Exclusion Criteria:

• Onset of complications that threat the life of the patient Inability to continue the diet Unwillingness to adhere the diet

The IPD would not share with other researchers.