Elsevier

Public Health

Volume 122, Issue 5, May 2008, Pages 509-515
Public Health

Original Research
Prevalence of overweight and associated factors in southern Brazilian adolescents

https://doi.org/10.1016/j.puhe.2007.08.002Get rights and content

Summary

Objective

The aim of this study was to determine the prevalence of overweight in adolescents in a southern Brazilian city, and ascertain gender differences and association with socio-economic and demographic conditions, family factors and individual behaviours.

Methods

Cross-sectional population-based study with random cluster sampling of households, including 722 adolescents (10–19 years), from a city in southern Brazil. Body mass index (BMI) was calculated based on the National Center for Health and Statistics reference curve, defining overweight as BMI ⩾85th percentile.

Results

Prevalence of overweight was 17% in girls and 19% in boys. In multivariate Poisson regression, chronic illness in parent(s) and household of up to four people were associated with overweight in boys, whereas low fibre intake, more hours spent watching television and regular exercise were associated with overweight in girls.

Conclusion

The prevalence of overweight in Brazilian adolescents is high, with gender differences in associated factors. Health workers in schools and public health services should be aware of these differences in order to improve preventive and therapeutic strategies in this age group.

Introduction

Overweight is associated with metabolic consequences that are a major impediment to quality of life in children and adolescents. In the USA, 32% of obese young people present with characteristics of metabolic syndrome1 and are considered to be a risk group for cardiovascular disease.2 Obesity in adolescents tends to persist into adulthood in 80% of cases and is associated with high morbidity.3

The prevalence of overweight in American adolescents is 30% according to the 1999–2000 NHANES.4 Prevalence is lower in developing countries such as Brazil, but is growing at a similar rate5, 6 as a result of the nutrition transition, as described in the literature.7 From 1975 to 2003, the prevalence of overweight in Brazilian boys and girls increased from 4% to 17.9% and 8.2% to 15.4%, respectively.8

The increase in overweight in adolescents could be due to any of the factors that influence energy intake or expenditure (dietary intake and physical activity) and family sociodemographic conditions. The cause of overweight is multifactorial and is influenced by the social, economic and physical environment in which the adolescent lives, including parental weight status, family income, parental education and number of people living in their household.9, 10, 11, 12

Recent studies have shown that overweight may be associated with reduced physical activity, such as school physical education, and increased sedentary activities, such as watching television. The relationship between physical activity and weight status appears to be gender specific, with girls reporting lower physical activity than boys, and some studies only showing an association between time spent watching television and obesity in girls.12, 13, 14, 15

Monteiro et al.10 studied adolescents from southern Brazil and demonstrated the importance of stratifying data from obesity studies according to sex. This study found that females from larger families and males from families with higher incomes were less likely to be overweight. However, few epidemiological studies have examined the associations between body mass index (BMI) and those factors stratified by sex, especially in Brazilian adolescents. The present study was designed to analyse the prevalence of overweight in adolescents in a city in southern Brazil, and to ascertain its association with socio-economic and demographic conditions, family factors and individual behaviours.

Section snippets

Methods

This was a cross-sectional, population-based study of adolescent residents of São Leopoldo, Rio Grande do Sul, Brazil. The sample size was based on an 18% assumed prevalence of overweight, 95% confidence intervals and statistical power of 80%, with 10% added for possible losses and 15% for multivariate analysis, resulting in a sample size of 807 subjects.

The study was approved by the Ethics Committee of the Federal University of Rio Grande do Sul, Brazil and written informed consent was

Results

In total, 810 eligible adolescents were identified in the selected households. The parents or the adolescents themselves declined consent in 8.6% (n=70) of cases, 1.8% (n=15) could not be located at home after three attempts, and 0.3% (n=3) had moved house, giving total losses of 11%. Losses were greater in males, accounting for 85% (n=60) of refusals.

Therefore, 722 adolescents were studied; 40.6% (n=293) were male and 59.4% (n=429) were female. The prevalence of overweight (BMI ⩾85th

Discussion

This study found a high prevalence of overweight in both genders, but different factors were associated with overweight in boys and girls. The prevalence of overweight was high in adolescents of all socio-economic categories, in contrast with a Brazilian population study performed in 198922 when it was predominant at higher socio-economic levels. The data from the present study are representative of the adolescent population from Brazil's southern and south-eastern states, where the last

Conclusion

This study found a high prevalence of overweight in adolescents, independent of maternal education. Hours spent watching television and fibre intake were shown to be associated with overweight in girls, while smaller households and presence of chronic illness in parent(s) were associated with overweight in boys. School and public health service health workers engaged in prevention and treatment of obesity in adolescents should therefore be aware of the gender-specific factors in development of

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