[Obesity, physical activity and inactivity among adolescents in Morelos, Mexico: a longitudinal study].

The prevalence of obesity in childhood and adolescence has increased in Mexico. This increase can be explained partly by a decrease in physical activity. The objective of this study was to assess the association between the prevalence of obesity and overweight with physical activity and inactivity among Mexican adolescents. We analyzed data from a longitudinal study with baseline and follow-up measures in 446 adolescents 12 to 17 years old, attending public schools in Cuernavaca, Morelos, Mexico. We collected information on weight, physical activity and demographic characteristics. Obesity and overweight were determined using as indicador the body mass index, and the cutoff points proposed by the International Obesity Task Force. The baseline prevalence of obesity or overweight was 37.22% (42.99% for males and 30.95% for females), and in the final measure 34.30% (38.46% for males and 32.28% for females). The median time of TV viewing was 3.90 h/d, with 0.73 h/d dedicated to vigorous physical activity and 0.58 h/d to moderate physical activity. Using logistic regression, after adjustment for obesity in the baseline measure, sex and clustering by school, we found no significant associations between the prevalence of obesity or overweight with time dedicated to TV viewing, vigorous or moderate physical activity. However, when conducting the analysis with an interaction term by sex, we found significantly lower risk of obesity or overweight associated with an increase in vigorous physical activity among males only (beta = 0.22, 95% CI (0.05, 0.89). Results suggest that vigorous physical activity may reduce the risk of obesity or overweight among male adolescents.