Overweight and obesity prevention for adolescents: a cluster randomized controlled trial in a school setting

Background: Given the increasing prevalence of obesity among youth over the past decade, prevention has become an international public health priority.

Purpose: To evaluate the 2-year effectiveness of three strategies aimed at preventing overweight and obesity among adolescents in a high school setting.

Design: PRomotion de l'ALIMentation et de l'Activité Physique (PRALIMAP) is a school-based RCT. Each study high school was assigned to receive or not, over a 2-year period (Grades 10 and 11), each of three prevention strategies according to a 2 × 2 × 2 factorial school randomization. Data were collected in 2006-2009 and analyzed in 2009-2011.

Setting/participants: A total of 3538 adolescents (aged 15.6±0.7 years at baseline) in 24 public high schools in Lorraine (northeastern France) completed the PRALIMAP trial.

Interventions: The prevention strategies were education (development of nutritional knowledge and skills); environment (creation of a favorable environment by improving availability of "healthy" dietary items and physical activity); and screening and care (detection of overweight/obesity and, if necessary, adapted care management).

Main outcomes measures: The main outcome of interest was BMI; BMI z-score and prevalence of overweight/obesity were considered as secondary outcomes.

Results: Adolescents who completed the PRALIMAP trial were younger, less often suspected of having eating disorders and depression, and came from a higher socioeconomic class than those who did not. The 2-year change of outcomes was more favorable in the 12 screening and care high schools compared to the no-screening ones: a 0.11 lower increase in BMI (p=0.0303); a 0.04 greater decrease in BMI z-score (p=0.0173); and a 1.71% greater decrease in overweight/obesity prevalence (p=0.0386). Education and environment strategies were not more effective than no strategy intervention.

Conclusions: Although the screening and care strategy is an effective way to prevent, at 2 years, overweight and obesity among adolescents in a high school setting, its effects over and above no strategy intervention were small.

Trial registration: This study is registered at www.clinicaltrials.govNCT00814554.