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.
Ketogenic diet treatment in adults with refractory epilepsy: a prospective pilot study.
To assess the efficacy of ketogenic diet (KD) in adults with refractory epilepsy.
                Eligible subjects were 18-45 years old with at least two monthly focal seizures (with or without secondary generalization) documented by 8 weeks' follow-up. Classic form of KD treatment (90% fat) was planned for 12 weeks: daily seizure diaries were kept and measurements of the urinary ketones were recorded. Blood studies were done monthly and resting energy expenditure (REE), substrate utilization; body composition and quality of life (QOL) were measured before and after intervention.
                Nine patients were enrolled (average age 28+/-6 years; seven women). Only two subjects concluded the study per protocol due to an early drop-out. The average length of KD treatment was 8+/-4 weeks (two patients completed 12 weeks of KD; feelings of hunger and lack of efficacy resulted in withdrawal of the rest). The two patients who concluded the study had a more than 50% reduction in the frequency of the seizures. The others experienced no improvement. Adherence to the KD protocol (100%) was documented by constant ketonuria and increased fat utilization as indicated by the change in respiratory quotient (p<0.031). The KD increased the cholesterol levels (mainly LDL; p=0.0001).
                In our experience with relatively small adult population, adherence to KD is difficult. In patients who had compliance over 3 weeks (6/8), KD does not seem to have a significant effect. Yet, the significant reduction in the two patients who concluded the study per protocol may indicate that some patients may benefit from this diet. Significant increase in LDL levels and the unlikable dietary changes are additional impediments to its implementation among adults with refractory epilepsy.