OBJECTIVE To compare the macronutrient intake of females with or without a history of anorexia nervosa (AN) at three times: two years and one year before the onset of AN, and during the first year of the illness. METHODS Prospective cohort study with 3-day food intake records collected over 10 years. Subjects were 154 white females (aged 9 or 10 years at study entry), of whom 14 had AN and 140 were healthy females matched for age at study entry and parental education. RESULTS Compared with the healthy girls, girls with AN reported significantly lower total energy intake and fat intake during the first year of the illness; the lower total energy intake was evident already at the 1-year (but not the 2-year) pre-onset assessment. CONCLUSIONS To identify AN early on, health practitioners caring for adolescent girls should inquire about food intake and reluctance to eat certain foods, especially those containing fat.