Reduced screen time leads to reduced BMI.

Decreasing the amount of television and other screen time was associated with a significant and sustained reduction in body mass index among overweight children aged 4-7 years, researchers reported.

In a randomized, controlled trial of 67 children, the use of automated devices that limited subjects' time using televisions, computer monitors, video game systems, DVDs, and VCRs to half of their usual allotment was linked to reduced sedentary behavior and a lower body mass index (BMI).

"Although the changes were modest, a small effect of this simple and inexpensive intervention (about $100 for each [device]) magnified across the population may produce important reductions in the prevalence of obesity and obesity-related comorbidities," said Leonard H. Epstein, Ph.D., of the State University of New York at Buffalo and his associates. The investigators studied children aged 4-7 years whose age- and sex-standardized BMI was at or above the 75th percentile for their age and sex. Most of these subjects were above the 85th percentile, and nearly half were above the 95th percentile. At baseline, the children had unlimited access to television-and computer-related sedentary activities in their homes.

A total of 35 children were randomly assigned to an intervention in which the automated devices monitored their week-by-week use of each TV and computer in the home. The devices turned these electronics off once the child had used up his or her weekly "allowance" of screen time. For each child, the allowance was set at 50% of their baseline viewing time.

Parents of children in this intervention group also received instruction on various strategies to encourage the children to decrease their screen time, and the children earned 25 cents for every half-hour under their screen "allowance" they achieved per week. Another 32 children who were assigned to the control group continued to have free access to television and computers in the home, but were encouraged to limit their screen time. Both groups were followed at 6-month intervals for 2 years.

Children in the intervention group decreased their screen time by 17 hours per week within the first 6 months and maintained that reduction throughout the study period. At the same time, their BMIs decreased significantly and remained lower throughout the 24 months of follow-up. In contrast, children in the control group decreased their screen time by 5 hours per week, and their BMIs did not decrease significantly.

The study subjects did not appear to increase their physical activity levels after their screens were turned off, but they did decrease the amount of food and drink they consumed. "Reducing television viewing could affect energy intake by minimizing cues to eat and by decreasing exposure to television advertising," Dr. Epstein and his associates said (Arch. Pediatr. Adolesc. Med. 2008;162:239-45).

The intervention worked best for families of lower socioeconomic status (SES), the researchers reported: "Children in lower SES families showed large and sustained BMI differences between the intervention and control families throughout the 2 years of measurement."

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BY MARY ANN MOON

Contributing Writer