ReviewThe effect of participation in school-based nutrition education interventions on body mass index: A meta-analysis of randomized controlled community trials
Highlights
► This MA shows that nutrition education is effective to reduce BMI among students. ► Intervention time is more relevant than the intervention component. ► The estimated effect size for the eligible RCTs was − 0.33 kg/m2. ► Among RCTs with more than one intervention year the effect size was − 0.48 kg/m2.
Introduction
From 1990 to 2010, the number of overweight children under five increased worldwide by an average of 0.8 million children per year. If the rate continues rising steadily until 2020, the number of overweight pre-school children on the planet will be 59.4 million, representing 9.2% of the entire population in this age group (de Onis et al., 2010, United Nations (UN), Department of Economic and Social Affairs, 2012).
The greatest increases in body mass occur in childhood and adolescence, and childhood overweight and obesity tend to persist into adulthood. Recognizing this fact, it is important to build healthy environments around strategic sites to protect children from psychosocial, metabolic and mechanical morbidities of overweight and obesity, as they constitute the fifth leading risk factor of global mortality (Freedman et al., 2005, Han et al., 2010, Hughes et al., 2011, Li et al., 2004, Lira et al., 2010, Nobre et al., 2006, Singla et al., 2010, Van Gaal et al., 2006, Wardle et al., 2006, World Health Organization (WHO), 2009).
The school environment has been considered a promising site for health promotion, as its organizational structure facilitates the development of interventions with multi-professional and multi-component approaches. School educational background allows both direct (e.g. classroom activities) and indirect (e.g. parental involvement) actions to protect children's health. In addition, children and adolescents dedicate a large portion of their time to school (Hughes et al., 2011, Pérez-Rodrigo et al., 2001, Silveira et al., 2011, Wardle et al., 2006, Wardle et al., 2007).
In this context, the aim of this review was to enhance the body of evidence, filling the gap left by past systematic reviews, regarding the effectiveness of school-based nutrition education interventions in reducing body mass index (BMI) in children and adolescents (Brown and Summerbell, 2009, Centre for Reviews, Dissemination (CRD), 2012, Gonzalez-Suarez et al., 2009, Jaime and Lock, 2009, Perez-Morales et al., 2009, Silveira et al., 2011, Zenzen and Kridli, 2009). To our knowledge, this is the first systematic review (SR) with a meta-analysis (MA) that exclusively includes randomized controlled trials (RCTs) that address school-based nutrition education, places no limits on the date of publication and uses BMI as the primary outcome.
Section snippets
Design and search strategy
This SR is part of a larger project called the “Physical Activity and Nutrition Education Systematic Review Project,” and the research protocol is registered at ClinicalTrials.gov (NCT00985972). The design followed the guidelines in Centre for Reviews and Dissemination: guidance for undertaking reviews in health care (CRD, 2008), and all stages of the study, including the MA, were carried out using the web-based software Eppi-Reviewer 3 (Eppi-Centre, Social Sciences Research Unit, Institute of
Search strategy
The search performed in the 14 databases, along with the cross-reference check of the 8 SRs, retrieved 4888 references, 3571 of which remained after checking for duplicates. Of 24 articles included in the qualitative synthesis (Silveira et al., 2011), 8 had sufficient data to be included in the MA (Fig. 1).
The qualitative synthesis considered studies reporting anthropometric and dietary (consumption of fruits and vegetables) outcomes. The 14 studies excluded due to outcome before the
Discussion
This is the first MA to exclusively investigate randomized community trials that assess the effectiveness of school-based nutrition education in reducing BMI among children and adolescents.
In our first research paper, we asserted that school-based nutrition education is able to reduce the prevalence of overweight and increase fruit and vegetable consumption (Silveira et al., 2011).
We presented a qualitative synthesis and chose not to proceed with a meta-analysis due to the high heterogeneity
Conclusion
Based on randomized controlled community trials, this systematic review provides evidence that school-based nutrition education interventions are effective in reducing BMI in children and adolescents, especially if the intervention duration is longer than one school year.
Conflict of interest
The authors declare that they have no conflicts of interest.
Acknowledgments
We would like to thank Dr. Alessandro Viggiano and Dr. Rebecca Muckelbauer for answering our emails with requested data. This project was funded by a grant from the Fundação de Amparo a Pesquisa de São Paulo (FAPESP) (protocol no. 09/12438-5). The author JS received a scholarship from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).
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