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.
Efficacy and tolerability of the ketogenic diet according to lipid:nonlipid ratios--comparison of 3:1 with 4:1 diet.
The ketogenic diet (KD) has been considered a highly potent antiepileptic treatment for intractable childhood epilepsy. In this study, we compared the antiepileptic efficacy and diet tolerability of two different diets with lipid:nonlipid ratios of 3:1 and 4:1.
                Seventy-six patients with refractory childhood epilepsy were randomly placed into two groups and were started on KD diets with nonlipid:lipid ratios of either 3:1 or 4:1. Antiepileptic efficacy and diet tolerability were evaluated 3 months after initiating the diet. Patients showing seizure-free outcome with the 4:1 diet were changed to the 3:1 diet, and those without a seizure-free outcome on the 3:1 diet were changed to the 4:1 diet, for three more months, after which time their progress was monitored.
                (1) Antiepileptic efficacy was higher for the 4:1 than the 3:1 diet (p < 0.05). Twenty-two (55.0%) of 40 patients on the 4:1 diet and 11 (30.5%) of 36 patients on the 3:1 diet became seizure free. Seizure reduction of over 90% was observed in 2 (5.0%) patients on the 4:1 diet, and 2 (5.6%) on the 3:1 diet. (2) Dietary tolerability was better for the 3:1 than the 4:1 diet. Gastrointestinal symptoms were observed in 5 (13.9%) patients with the 3:1 diet and 14 (35.0%) patients with the 4:1 diet (p < 0.05). (3) For seizure-free patients who started on the 4:1 diet, antiepileptic efficacy was maintained after changing to the 3:1 diet, while 10 (83.3%) of 12 patients who were not seizure free with the 3:1 diet showed increased seizure reduction after changing to the 4:1 diet. (4) Complications from the KD and laboratory data were not significantly different between the two groups.
                The 4:1 KD showed greater antiepileptic efficacy than the 3:1 diet with higher seizure-free outcome. In most cases, seizure free outcome was maintained even after changing the ratio to 3:1. Dietary tolerability was better in the 3:1 diet than the 4:1 with less frequent gastrointestinal symptoms.