This study will provide a comprehensive assessment of long-term treatment with the ketogenic diet, a medical diet with high fat and low carbohydrate intake, focusing on safety and cardiovascular implications. We will assess patients with epilepsy or one of two rare metabolic diseases; glucose transporter type 1 deficiency syndrome (GLUT1 DS) or pyruvate dehydrogenase complex deficiency (PDHD).

Inclusion Criteria:

• Treatment with the ketogenic diet at the National Centre for Epilepsy (SSE) for 5 years or more
• Able to travel from The National Centre for Epilepsy - SSE (Sandvika) to Rikshospitalet (Gaustad) to perform procedures to investigate cardiovascular risk factors
• Willing to draw extra blood for research purposes
• Willing to sign informed consent and participate in the study in accordance with the study protocol
• Willing to sign informed consent for blood samples to be included in research biobank at the Department of Neurology, Oslo University Hospital

Exclusion Criteria:

• Non-compliance with the dietary treatment for 6 months or longer or more than once per month
• Not possible to communicate with parents in Norwegian or English without interpreter
• Patient not able to cooperate and lie still for about ten minutes during the carotid ultrasound examination
• Psychiatric/mental illness, alcohol or drug abuse or other factors making it impossible to pursue the study protocol

Patients treated with the ketogenic diet (classical or modified) for epilepsy, GLUT1 deficiency or PDHD at The National Centre for Epilepsy - SSE for 5 years or longer.