Approximately 43 million people in the United States, or 14% of the population, are 10 to 19 years old.¹ Outside of the first year after birth, adolescence is the period of greatest growth and development across the life span. Longitudinal height increases 20%, body weight doubles, 40% to 60% of peak bone mass is accrued, muscle mass increases, blood volume expands, and the heart, brain, lungs, liver, and kidney all increase in size. As a result, nutritional requirements increase dramatically, and many adolescents consume inadequate amounts of vitamins, minerals, and nutrients for their needs (including folic acid; vitamins A, D, E, and B₆; calcium; iron; zinc; magnesium; and fiber) as well as foods from several important groups, such as fruits, vegetables, and whole grains.^2,3,4,5 Adolescent diets also frequently exceed recommendations for fat, saturated fat, sodium, and cholesterol. Furthermore, a substantial number of teenagers frequently eat energy-dense foods (such as fast food and sugar-sweetened beverages), are physically inactive,^5,6 and gain an excessive amount of weight.⁷ Additional factors, such as pregnancy, chronic disease, and physical conditioning, increase nutritional requirements of the adolescent. Some disorders that develop during adolescence, such as eating disorders, obesity, and chronic illnesses, are associated with either insufficient or excessive nutrient intake.