The increased prevalence of obesity in the last decades has
turned obesity into the most frequent nutritional disorder in
developed countries (Daniels et al., 2005).
Genetic and environmental factors determine the risk of being
overweight in a predisposed subject. However, environmental
factors (including energy and food intake, psychosocial aspects,
eating and physical activity habits) have a larger impact on the
increase of obesity prevalence (Moreno and Rodriguez, 2007;
Rodriguez and Moreno, 2006).
During these decades of rising obesity prevalence, physical
activity among children and adolescents has declined, while
time spent in sedentary activities such aswatching television and
playing computer games has increased (Daniels et al., 2005). In
parallel, in nationally representative samples of US children