Increased television viewing is associated with elevated body fatness but not with lower total energy expenditure in children

Background: Television (TV) viewing in children is associated with a higher body mass index, but it is unknown whether this reflects body fatness, and, if it does, why. Objective: The objective was to investigate whether TV viewing is associated with body fatness, physical activity, and total energy expenditure in preschool children. Design: Eighty-nine children were recruited into a cross-sectional study. Total daily energy expenditure (TEE) was measured by doubly labeled water, body composition by dual-energy X-ray absorptiometry, and physical activity by accelerometry. Results: There was a significant positive association between fat mass (corrected for fat-free body mass) and TV viewing (F = 9.05, P = 0.004). Each extra hour of watching TV was associated with an extra 1 kg of body fat. Children who watched more TV were also significantly less physically active (F = 5.16, P = 0.026). Independent of body composition and sex, children with greater physical activity levels had higher TEE (F = 5.15, P = 0.029); however, physical activity did not mediate the relation between TV viewing and adiposity (P > 0.05). Conclusions: Preschool children who watch more TV are fatter and are less active, and activity influences TEE. However, despite TV viewing being linked to lower physical activity, the relation between TV viewing and fatness is not mediated by physical activity. The results suggest that a relation between TV viewing and fatness is more likely to be due to an effect on food intake. Am J Clin Nutr 2009; 89: 1031