Born to treat epilepsy in children, the ketogenic diet now intrigues neurologists in the face of Alzheimer's, Parkinson's and multiple sclerosis. Can it really offer emergency fuel to the aging brain? As the years pass, the brain gradually loses its energy efficiency. In some people, this fragility opens the way to neurodegenerative diseases. What if part of the answer was on the plate? Long reserved for the treatment of childhood epilepsy, the ketogenic diet is now attracting the attention of neurologists. A large scientific review suggests that it may help the brain circumvent certain age-related energy breakdowns.