If participants agree to be in this study, the investigators will ask the participants to do the following things:

At Initial enrollment for both longterm ketogenic diet and new modified Atkins diet participants

Review of calendars (showing seizures) and 3-day food record

Check height and weight, blood pressure, skin-fold thickness and waist circumference

Standard modified Atkins diet clinic labs will be drawn as well as levels of low density lipoprotein (LDL) fractions, fatty acids, and apolipoproteins B and A-1

Participant will receive a high-resolution ultrasound of the carotid arteries in the neck performed either the day of enrollment or within 1 month of enrollment

At follow-up clinic visits (month 3 and month 6) for new modified Atkins diet participants

Review of calendars and food records

Labs repeated - standard modified Atkins diet clinic labs as well as levels of low density lipoprotein (LDL) fractions, fatty acids, and apolipoproteins B and A-1

Check height and weight, blood pressure, skin-fold thickness and waist circumference

At follow-up clinic visits (month 12 and month 24) for new modified Atkins diet participants