When the body burns (metabolizes) fat, it creates substances called ketones. The ketogenic diet tries to force the body to use more fat for energy instead of sugar (glucose) by increasing fat and restricting carbohydrates. The ketogenic diet can be used to prevent seizures in an adult or a child who has any type of epilepsy. It is not yet clear how or why the ketogenic diet prevents or reduces seizures.
One version of the ketogenic diet provides 4 grams of fat for every 1 gram of protein and carbohydrate together. People on a ketogenic diet have to eat mostly fatty foods, such as butter, cream, and peanut butter. Foods such as bread, pasta, fruits, and vegetables have to be severely limited. And the person's total calories are also restricted. At every meal, the food has to be measured carefully so that the right amounts of each food are given. Even a slight departure from the diet can cancel its effect.
If you are thinking about the ketogenic diet, keep in mind:
- For the diet to prevent seizures, your child has to follow it exactly. The amounts and types of foods eaten have to be measured precisely. And preparing meals can take a lot of time.
- The diet does not work for some children, no matter how closely they follow it.
The ketogenic diet is very strict and can be hard for some people and families to follow. Other special diets for epilepsy that are less strict may also be tried.
- The medium chain triglyceride (MCT) diet. People on this diet take an oil supplement instead of relying on food for the fat in the diet. This can make the diet easier, because less total fat is needed from food and the person can eat more protein and carbohydrates.
- The modified Atkins diet. The Atkins diet is known as a high-protein, low-carbohydrate diet. The modified Atkins diet for people with epilepsy is similar to the ketogenic diet but allows for a little more flexibility in protein, fluid, and calorie amounts.
- The low glycemic index. This is the least restrictive special diet for epilepsy. It does not restrict fluids or protein and people do not need to be so strict about calories or the amount of fat they eat. People on this diet still eat much more fat than in a typical diet, but carbohydrates are not as limited.
What To Expect
A person usually has to fast the day and night before starting the diet. The diet is gradually introduced over several days, so that the body can get used to the dramatic change. The person may feel tired and lack energy during the first few days.
Children are usually admitted to a hospital or epilepsy center when they start the diet. There, the child can be watched and parents and caregivers can get training on how to do the diet at home. The ketogenic diet should always be given under the supervision of a doctor and a dietitian.
When it works, the ketogenic diet works quickly to reduce seizures. People usually start having fewer seizures in 2 to 3 weeks. In 2 to 3 months you will be able to tell how well it is working.
Why It Is Done
The ketogenic and other diets may sometimes be used to treat people who have severe seizures and who have not responded to antiepileptic medicines.
How Well It Works
After 6 months on the ketogenic diet, 30% to 60% of children had half as many seizures as they had before going on the diet.footnote 1
Evidence shows that the ketogenic diet works about as well as medicines to control seizures in children.footnote 2 There is less evidence for special diets in adults with epilepsy, but a modified version of the Atkins diet may work as well as the ketogenic diet to control seizures.footnote 2
Special diets for epilepsy are not considered healthy, and they can have side effects. Some of the side effects make it hard to continue the diet. Side effects include:
- Digestive problems, such as diarrhea, constipation, nausea, vomiting, and heartburn.
- High cholesterol (some people may need to take medicine).
- Kidney stones.
- Low energy levels.
- Slower growth rates in children.
- Vitamin and mineral deficiencies which can be helped by taking supplements.
Everyone on the diet needs close supervision by a doctor and a dietitian.
What To Think About
The ketogenic diet is very strict and can be hard for some people and families to follow.
- Lee PR, Kossoff EH (2011). Dietary treatments for epilepsy: Management guidelines for the general practitioner. Epilepsy and Behavior, 21(2): 115–121. DOI: 10.1016/j.yebeh.2011.03.008. Accessed May 19, 2016.
- Levy RG, et al. (2012). Ketogenic diet and other dietary treatments for epilepsy. Cochrane Database of Systematic Reviews (3).
Current as of: March 28, 2019
Author: Healthwise Staff
Medical Review:John Pope, MD, MPH - Pediatrics & Kathleen Romito, MD - Family Medicine & E. Gregory Thompson, MD - Internal Medicine & Martin J. Gabica, MD - Family Medicine & Steven C. Schachter, MD - Neurology