THE INFLUENCE OF PHYSICAL ACTIVITY AND SEDENTARY BEHAVIOURS ON BODY MASS INDEX FROM CHILDHOOD TO ADOLESCENCE

The prevalence of overweight and obesity among children and adolescents is rising in the European region with an increase of the onset of risk factors associated with ill health (1). Time spent in sedentary (SED) behaviour and physical activity (PA) have been both associated with adiposity (2, 3). The aim of this study was to investigate the influence of physical activity and sedentary behaviours from childhood (CH) to adolescence (AD). METHODS: The study population consisted of 2828 students aged between 6 and 14 years old (height, 1,45±0,16 m; weight, 39,6±12,7 kg; BMI, 18,3±3,0 kg/m2) and was divided into two groups: CH and AD. Subjects were classified as normal weight (NW), overweight (OW) and obese (OB) according to Cole classification (4). Parents were asked to fill a questionnaire inquiring about time spent in PA, and SED behaviours outside school hours on a weekly basis. The amount of PA was evaluated adding leisure time PA, time spent playing sports and time spent in physically active commutes to and from school. SED activities included TV viewing, playing or working on a computer/playing videogames and any other sedentary activities. A multiple logistic regression analysis, adjusted for sex and age, was used to assess the association between BMI category and PA or SED; significance was set at p<0,05. RESULTS: 79,9% of the cohort was classified as NW, 17,1% as OW and only 3,9% as OB. Overweight and obesity significantly decreased from CH to AD (X2=33,45; p<0,0001). The average amount of PA was 245,5±152,2 min/week and the SED time reached 1739,1±809,7 min/week, both significantly increasing from CH to AD (ANOVA; p<0,0001). PA was not significantly correlated with SED in neither CH nor AD (r=-0,031 and 0,024; respectively). Significant associations, were identified between SED (odds ratio (OR): 1,001; 95%CI: 1,000-1,001; p<0,001) and PA (OR: 0,997, 95%CI: 0,996-0,999; p<0,01) level and obesity. No associations persisted for overweight. DISCUSSION: According with Mitchell (2,3) this study’s data indicated that: I) more time spent in PA was negatively associated with obesity; II) spending more time in sedentary behaviour was associated with obesity. In conclusion, increasing the time spent in physical activities and reducing time spent in sedentary behaviours may help to reduce the prevalence of childhood and adolescent obesity. REFERENCES: (1) Branca (2007). World Health Organization. (2) Mitchell (2013). Obesity, Mar;21(3):E280-93. (3) Mitchell (2013). Int J Obes, Jan;37(1):54-60. (4) Cole (2000). BMJ, May 6;320(7244):1240-3.