Avaliação do papel de fatores psicossociais na atividade física e sedentarismo de adolescentes.

Abstract

This thesis has as main objective to evaluate the role of psychosocial factors on physical activity and sedentary in adolescents. To accomplish this we developed two manuscripts, using data from the Longitudinal Study of Adolescent Nutritional Assessment - ELANA, conducted in four private and two public schools in the metropolitan area of Rio de Janeiro. This thesis refers to the cohort of 810 elementary school students who participated in the baseline study in 2010, and the follow-up in 2012. The first manuscript evaluated the role of psychological well-being, development and persistence of the practice moderate and vigorous physical inactivity (MVPA) and excessed time spent in front of the screen, after two years. Girls with worse psychological state at baseline had higher risk of spending too much time in front of the screen watching TV, playing video games and using computers, two years later. Also in girls, the psychological state influenced the practice of MVPA; those with worse psychological state had a higher risk of physical inactivity after two years of follow-up. In the second manuscript was investigated by means of structural equation models, stability and direction of associations between body bullying and a set of health-related behaviors and state (MVPA, time spent per day with television (TV), video game and computer (VG), body mass index (BMI)), during adolescence, stratified by gender. The bidirectionality of these associations was observed among boys. Those most bullied at baseline were spending more time VG two years later. Additionally, overweight adolescents at baseline appeared to be bullied in the following. Among the girls, the bidirectionality was not found; only was observed that those who suffering more previous provocations spent more time with VG two years later. We concluded that psychosocial factors influenced the health-related behavior and state investigated, differently for boys and girls. The time spent on sedentary activities across the screen and MVPA were influenced by the psychological well-being among girls. The bidirectionality of the relationship between body provocations and health-related behaviors/ status was observed among boys and among girls only the causal direction of provocations in the baseline affecting VG time following was found. A better understanding of the determinants that affect behavior and conditions related to health and how such behaviors/ status are associated with body provocations, can support public health and educational managers actions with a view to promoting a healthier school environment, and assist in the prevention and control of situations that favour a worse psychological state, physical inactivity, sedentary lifestyle and overweight / obese adolescents.