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.
A prospective study of the modified Atkins diet for intractable epilepsy in adults.
The ketogenic diet is not typically offered to adults with epilepsy due to the significant lifestyle alterations needed for its use. The modified Atkins diet has been recently demonstrated to be therapeutic for children without the need for an admission, fasting period, weighing of foods, or fluid, calorie, and protein restriction.
                A prospective, open-label study was performed of adults over 18 years of age, having at least weekly seizures and prior use of at least two anticonvulsants. Carbohydrates were initially restricted to 15 g/day, fats were encouraged, and fluids, protein, and calories were allowed ad lib.
                Thirty patients, with age ranging from 18 to 53 years, were enrolled. Using an intent-to-treat analysis, 47% had a >50% seizure reduction after 1 and 3 months on the diet; 33% after 6 months. In those with seizure reduction, the median time to improvement was 2 weeks (range: 1-8 weeks). The mean weight loss was 6.8 kg, p < 0.001. Body-mass index (BMI) decrease correlated with efficacy at 3 months, p = 0.03. Ten subjects (30%) discontinued the diet prior to 3 months. Side effects included increased cholesterol (mean 187 to 201 mg/dL), blood urea nitrogen (BUN; 13 to 16 mg/dL), and urine calcium to creatinine ratio (0.14 to 0.19).
                A modified Atkins diet appears to demonstrate preliminary efficacy for adults with intractable epilepsy, especially in those who lost weight. Considering the rapid response in those who improved, but somewhat high discontinuation rate, a 2-month trial period may be adequate to assess for efficacy.