Glucose transporter type 1 deficiency syndrome is an inborn error of glucose transport across the blood-brain barrier with hypoglychorrachia. Patients usually present developmental delay, movement disorders, seizures, and acquired microcephaly, variously associated and leading to different phenotypes. We report a 3-year-old girl affected by glucose transporter type 1 deficiency syndrome with carbohydrate responsiveness. Her history was characterized by worsening of ataxia with an increasing interval to the last food intake, occurrence of seizures in the morning before breakfast, slowing of electroencephalogram (EEG) background activity with the appearance of epileptiform discharges during preprandial recordings, and improvement of the electroclinical picture after food intake. By adding a new case to the pertinent literature, we stress the role of pre- and postprandial EEG recordings for the identification of individuals potentially affected by glucose transporter type 1 deficiency syndrome. We also provide a possible physiopathological interpretation of EEG changes related to food intake.