Our review update included data from four new randomised studies of the ketogenic diet. Although none were blinded, some were of good quality. These studies suggest that in children, the ketogenic diet results in short to medium term benefits in seizure control, the effects of which are comparable to modern antiepileptic drugs. However, one study of long term outcome reports a high attrition rate for the diet. This would suggest that many children find the diet difficult to tolerate. The main reasons for drop-outs in the included studies included gastrointestinal side effects and dislike for the diet.
We found just three studies on the use of the diet in adults and none of these were randomised. There has been less research involving other diets. We found one randomised study of reasonable quality of the Atkins diet. This study showed similar benefits in seizure control with a less restrictive diet.
For those with medically intractable epilepsy or those in whom surgery is unsuitable, a ketogenic diet could improve seizure control, but tolerability is poor. One observational study suggested that the Atkins diet may have a similar effect on seizure control, but this requires more investigation.
The ketogenic diet: a 3- to 6-year follow-up of 150 children enrolled prospectively.
To document the long-term outcome of the 83 children with difficult-to-control seizures who were enrolled prospectively in a study of the efficacy of the ketogenic diet and who had remained on the diet for 1 year.
                A total of 150 consecutive children were entered prospectively into a study of the ketogenic diet's efficacy and tolerability. Three to 6 years after diet initiation, all 150 families were sent a survey inquiring about their child's current health status, seizure frequency, and current anticonvulsant medications. They were asked about their experience with the diet and reasons for discontinuation. Several telephone attempts were made to contact those who did not respond to the written questionnaire. Responses were entered in an Access database and analyzed.
                In 1999, 3 to 6 years after initiating the diet, 107 of 150 families responded to a questionnaire. Thirty-five additional families were interviewed by telephone, 4 were lost to follow-up, and 4 children had died, unrelated to the diet. Of the original 150 patient cohort, 20 (13%) were seizure-free and an additional 21 (14%) had a 90% to 99% decrease in their seizures. Twenty-nine were free of medications, and 28 were on only 1 medication; 15 remained on the diet. There were no known cardiac complications.
                Three to 6 years after initiation, the ketogenic diet had proven to be effective in the control of difficult-to-control seizures in children. The diet often allows decrease or discontinuation of medication. It is more effective than many of the newer anticonvulsants and is well-tolerated when it is effective.