The authors tested the hypothesis that consumption of whole grain is associated with greater insulin sensitivity and lower body mass index (BMI) (weight (kg)/height (m)(2)) in adolescents and that this association is stronger among the heaviest adolescents. Two 127-item food frequency questionnaires were administered at the mean ages of 13 years (standard deviation 1.2) and 15 years (standard deviation 1.3) to 285 Minnesota adolescents who underwent two euglycemic insulin clamp studies 2 years apart as part of a protocol evaluating the influence of insulin resistance on development of adverse cardiovascular disease risk factors. Intake of whole grain was examined for associations with BMI and insulin sensitivity (measured as milligrams of glucose uptake per kilogram of lean body mass (M(lbm)) per minute). After adjustment for age, gender, race, Tanner stage, and energy intake, mean BMI was 23.6 for adolescents consuming less than serving/day of whole-grain foods, 22.6 for -1 servings/day, and 21.9 for more than 1 servings/day (p = 0.05). After adjustment for age, gender, race, Tanner stage, energy intake, BMI, and physical activity, M(lbm) was 11.6, 12.3, and 13.2 mg/kg/minute, respectively, in the three whole grain intake groups (p = 0.02). This relation was stronger among adolescents with higher BMIs (p = 0.001). Whole grain intake was associated with greater insulin sensitivity and lower BMI in adolescents, especially among the heaviest persons.