Obesity among children attending elementary public schools in São Paulo, Brazil: a case–control study

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Abstract
Objectives: To describe obesity among students of public schools in Sao Paulo and to identify risk factors for this nutritional and physical activity disorder. Design: Case-control study of obese and non-obese schoolchildren to study risk factors for obesity. Setting: Anthropometric survey including 2519 children attending eight elementary public schools in Sao Paulo, Brazil. Subjects: Schoolchildren aged 7-10 years, of whom 223 were obese (cases; weight-for-height greater than or equal to two standard deviations (greater than or equal to 2SD) above the median of the National Center for Health Statistics (NCHS) reference population) and 223 were eutrophic (controls; weight-for-height +/-1SD from NCHS median). Measurements: Parents or guardians of the 446 cases and controls were interviewed about the children's eating behaviours; and habits. Results: The prevalence of obesity (weight-for-height greater than or equal to2SD) in the surveyed population was 10.5%. A logistic regression model fitted to the case-control dataset showed that obesity was positively associated with the following factors: birth weight greater than or equal to3500g (odds ratio (OR) 1.83, 95% confidence interval (CI) 1.21-2-78), child's appetite at meals (OR 3.81, 95% CI 2.49-5.83), watching television for 4 h per day or longer (OR 2.07, 95% CI 1.32-3.24), mother's schooling >4 years (OR 1.85, 95% CI 1.25-2.75) and parents' body mass index greater than or equal to30 kg m(-2) (OR 2.50, 95% CI 1.43-4-37). Conclusion: The explanatory multivariate model points to preventive measures that would encourage knowledge of the children and their guardians in relation to a balanced diet and a less sedentary lifestyle, such as reducing television viewing. Schoolchildren with a birth weight of 3500 g or more or whose parents are obese should receive special attention in the prevention of obesity.