Associations of diet and physical activity with body mass index, body fat and waist circumference in Azorean adolescents

Abstract

According to the World Health Organization, the high prevalence of childhood obesity is a serious public health problem that can be observed in developed and developing countries alike. Although obesity in children and adolescents entails numerous morbidities, the major health problem will be seen in the next generation, since an obese child is most likely to be an obese adult. Among the factors associated with obesity, it is described that diet and physical activity play key roles in the development of this condition. Concerning diet, recent studies suggest that the consumption of dairy products may protect against obesity. In this context, the objective of this study was to determine the association between diet, particularly the intake of dairy products, physical activity and the occurrence of excessive body mass index, waist circumference and/or percent body fat in adolescents. Thus, we carried out a school-based study, "The Azorean Physical Activity and Health Study II," with a representative sample of 1,515 Azorean adolescents (15 to 18 years old). Anthropometric measurements, such as weight, height, waist circumference and percent body fat, were collected according to standard protocols. Data on sociodemographic and lifestyle features were assessed by a questionnaire. Dietary and nutritional intake were measured via a self-administered semi-quantitative food frequency questionnaire. Physical activity was assessed via a self-report questionnaire by Telama et al. (1997). The Kolmogorov-Smirnov test was used to assess the assumption of normality. Independent sample t or Mann-Whitney tests and one-way analysis of variance or Kruskal-Wallis tests were performed to compare continuous variables. The Chi-square test was used with categorical variables. We also used regression models (multiple linear and logistic) to estimate the association between diet, physical activity and components of obesity. Thus, we highlight as our main results: higher intake of milk and ready-to-eat cereals, as well as father's employment status, seem to have an inverse association with abdominal obesity; physical activity levels are lower in adolescents with abdominal obesity; milk intake seems more likely to be inversely associated with components of obesity than do yogurt and cheese intake; and high milk intake seems to have a protective effect against abdominal obesity, regardless of physical activity level.