The first paper on the application of the medical ketogenic diet in epilepsy was published in 1921. The interest in the diet has increased significantly in the past decades. In 2018, the second consensus guideline on the ketogenic diet was published, including clinical practice and dietary management. In 2021, the ketogenic diet in epilepsy is a mainstay nonpharmacological management option, applied in infants, children and adults with epilepsy. New research is gearing towards new onset epilepsy, prescription in refractory Status Epilepticus and an increasing number of neurological disorders, beyond epilepsy.