Sixteen non-overweight children (aged 12-16years) were studied during three separate three-week periods: 1) baseline, 2) increasing targeted sedentary behaviors by 25-50% (increase phase), and 3) decreasing targeted sedentary behaviors by 25-50% (decrease phase). Sedentary behavior was defined as activities such as watching television or videotapes, playing video games, and recreational computer use. Compared with baseline, targeted sedentary behaviors increased by 81.5 minutes/day (45.8%) during the increase phase and decreased by 109.8 minutes/day (-61.2%) during the decrease phase. Mean energy intake decreased by 463 kcal/day (p < 0.01) during the decrease phase. No significant changes in energy intake were observed during the increase phase. Decreasing sedentary behaviors also resulted in a mean increase of energy expenditure of 113 kcal/day.

Comment: These findings indicate that a decrease in sedentary behaviors is accompanied both by a decrease energy intake and an increase in energy expenditure in non-overweight adolescents. Reducing the amount of time involved in watching television and playing on the computer would therefore be expected to help prevent the development of obesity.

Epstein LH, et al. Influence of changes in sedentary behavior on energy and macronutrient intake in youth. Am J Clin Nutr 2005;81:361-366.