A randomized controlled trial of students for nutrition and eXercise: a community-based participatory research study

Abstract

Purpose: To conduct a randomized controlled trial of Students for Nutrition and eXercise, a 5-week middle school-based obesity-prevention intervention combining school-wide environmental changes, multimedia, encouragement to eat healthy school cafeteria foods, and peer-led education.

Methods: We randomly selected schools (five intervention, five waitlist control) from the Los Angeles Unified School District. School records were obtained for number of fruits and vegetables served, students served lunch, and snacks sold per attending student, representing an average of 1,515 students (SD = 323) per intervention school and 1,524 students (SD = 266) per control school. A total of 2,997 seventh-graders (75% of seventh-graders across schools) completed pre- and postintervention surveys assessing psychosocial variables. Consistent with community-based participatory research principles, the school district was an equal partner, and a community advisory board provided critical input.

Results: Relative to control schools, intervention schools showed significant increases in the proportion of students served fruit and lunch and a significant decrease in the proportion of students buying snacks at school. Specifically, the intervention was associated with relative increases of 15.3% more fruits served (p = .006), 10.4% more lunches served (p < .001), and 11.9% fewer snacks sold (p < .001) than would have been expected in its absence. Pre-to-post intervention, intervention school students reported more positive attitudes about cafeteria food (p = .02) and tap water (p = .03), greater obesity-prevention knowledge (p = .006), increased intentions to drink water from the tap (p = .04) or a refillable bottle (p = .02), and greater tap water consumption (p = .04) compared with control school students.

Conclusions: Multilevel school-based interventions may promote healthy adolescent dietary behaviors.

Trial registration: ClinicalTrials.gov NCT01914471.

Keywords: Adolescent obesity; Community participation; Eating; Intervention studies; Schools.

Figure 1

Percentage Changes in Cafeteria Outcomes Associated with Intervention, Relative to Expected Change in the Absence of Intervention (During and After the Intervention). Note: Bars represent the change in the outcome during (black) and after (grey) the intervention relative to what would be expected in the absence of intervention – that is, if the intervention schools experienced the same changes observed in control schools. For example, during the intervention, the average intervention school increased fruit servings from .453 to .539 servings per attending student, an increase of about .086 servings per student. During the same period, the average control school increased fruit servings by about .014 servings per student, meaning that intervention schools, relative to control schools, increased fruit servings by .086 - .014 = .072, and that in the absence of an intervention we would have expected the intervention schools to increase to .453 + .014 = .467. Therefore the effect of the intervention was a (.072 / .467) = 15.3% increase in fruit servings per attending student.