Promoting healthful diet and physical activity in the Mexican school system for the prevention of obesity in children.

Objective: This paper describes the rationale, design, and methods of a two-year randomized controlled trial conducted to evaluate the effectiveness of an environmental intervention in 27 elementary schools in Mexico City.
Materials and Methods: There were two units of analysis, school level addressing changes in elementary public part-time schools, and individual-level addressing behavioral changes in students 9 to 11 years of age. Two intensities of an intervention program were implemented (basic and plus), each containing two intervention components: physical activity and nutrition, supported by a communication/education component. Evaluation of the intervention was carried out during the school cycles 2006-2007 and 2007-2008.
Results: Primary outcomes were overweight and obesity prevalence and fitness; environmental and behavioural measures were also examined.
Conclusions: This is the first institutional multilevel, multifactorial project, consistent with the best practices available in current literature, carried out in Mexico to prevent childhood obesity in schools.