Research studies have clearly shown that adolescents' dietary intakes are not consistent with national recommendations. Areas of concern include high intakes of saturated fat, total fat, and soft drinks, and low intakes of fruits, vegetables, fiber, and calcium-rich foods [1–3]. These dietary patterns are of concern because of their potential for increasing risk for developing obesity, heart disease, osteoporosis, dental caries, and various types of cancer .
Adolescent eating patterns are influenced by factors proximal to the adolescent such as individual food preferences , family meal patterns , and parental role modeling . However, it is increasingly becoming clearer that adolescent eating patterns are also influenced by more distal factors such as media messages and social norms [8, 9]. Since adolescents spend a large amount of time in school, an important question – is to what extent does the school food environment influence adolescent eating patterns . In Bronfenbrenner's ecological model, which shows concentric spheres of influences on the individual ranging from proximal factors (i.e., individual characteristics) to distal factors (i.e. social norms and public policies), the school lies in the middle .
Although there are federal regulations regarding the types of foods that can be served in the United States Department of Agriculture (USDA) reimbursable school meals [12, 13], few regulations are in place for alternative foods, such as those served a la carte in the cafeteria or in snack bars, and in vending machines . A study of 55 high schools revealed that school environments do not always foster healthful eating practices consistent with national dietary guidelines . In a statewide survey of food policies in 336 Minnesota high schools, two-thirds of the principals indicated that only healthy food choices should be provided to students at school, yet only one-third reported that their school had an overall policy about nutrition and food. Even fewer reported the presence of specific policies about the types of foods and beverages sold in vending machines, school stores, or at school functions . School vending machines were prevalent and 77% of the principals reported that their school or district had a contract with a soft drink company. Vending machine hours were limited in some way in 81% of the schools, but only about a third of the schools limited the vending machine hours to before and after school only or after all lunch periods were completed. While it is important to respect adolescents increasing autonomy and decision-making skills, research clearly shows that food availability is one of the strongest correlates of food choices in adolescents [17, 18]. Schools provide a setting in which it is possible to increase the availability and attractiveness of a range of healthy food options from which students can make choices, and restrict the availability of foods that are low in nutrients and high in fats and sugars.
The few studies that have examined associations between school food environment and student eating patterns suggest that the school food environment has a significant impact on food choices. Cullen and colleagues  found that fourth grade students attending elementary schools without a la carte food items consumed more fruits, juices, and vegetables than fifth graders who attended a middle school with a la carte food line (or snack bar). Kubik et al found that among seventh-grade students in 16 schools, having a school a la carte program was associated with lower intakes of fruits and vegetables and higher intakes of calories from total and saturated fats . They also found that the number of snack vending machines was associated with lower fruit intakes, suggesting that students may be choosing alternative snack foods from the vending machines rather than fruit. However, policies were not examined regarding the types of foods sold in vending machines and their hours of operation and the impact of such policies on vending machine purchases.
This study expands on the limited, but growing, body of literature that explores the role of schools in influencing the dietary practices of youth. Specifically, our study objectives are: 1) to describe school lunch practices and vending machine purchases in a large sample of high school students; and 2) to examine associations between eating patterns of high school students and school food environment and policies.