 A systematic review in 2012 found and analysed four randomized controlled trials of ketogenic diet in children and young people with epilepsy , as well as six prospective and five retrospective studies . The trials were done among children and young people for whom drugs failed to control their seizures , and only one of the trials compared a group assigned to ketogenic diet with a group not assigned to one . The other trials compared types of diets or ways of introducing them to make them more tolerable . Nearly 40 % of the children and young people had half or fewer seizures with the diet compared with the group not assigned to the diet . Only about 10 % were still on the diet after a few years . Adverse effects such as hunger and loss of energy in that trial were common , with about 30 % experiencing constipation . 
