The answer is complicated. There is a universe of seizures that apparently respond well to dietary intervention and many that do not. Seizures have different etiologies. Bear in mind that there is cumulative brain damage with each seizure, and that under many circumstances the event would endanger your life and/or the lives of others. Proceed with great caution.
A Ketogenic Diet (high fat, adequate protein, low carbohydrate diet) is highly recommended. This diet is also called the LCHF (low carb high fat) diet (see the blog Diet Doctor for more info). I eat the LCHF diet and my cholesterol, LDL, HDL and triglycerides are all in optimal range, i'm losing weight and improving my insulin resistance. It's a diet that can help more than seizures. :)
"After 4 weeks we weaned his Depokote and put him on Zonegram. That didn't help either. Nathan was started on a diet for Seizure control...Ketogenic Diet. He had his last grand mal seizure the 3 day on the diet. His muscle and drop seizures ended 2 months later completely, but we noticed they were less harsh with each one he had til they just stopped." - excerpt from KetoGenic Diet for Seizures.