A study by researchers at Johns Hopkins University School of Medicine, along with experts at the CDC and the National Institutes of Health, concludes that a child's weight increases with the number of hours he or she spends watching television each day. These experts are calling a US "epidemic" of childhood obesity. Many US children watch a great deal of television and are inadequately vigorously active.

The researchers discovered that 20% of US children partake in two or fewer bouts of vigorous activity per week. (Health experts currently recommend at least three periods of strenuous exercise per week). The problem stems from the fact that watching television is a sedentary activity -- but it's much more than that. Children are watching TV, many times eating high-calorie/high-fat snack foods, and watching commercials for fast food, all of which may encourage more eating.

The study also showed that 26% of US children watched 4 or more hours of television per day. Experts already label television viewing as the number one leisure-time activity of most school-age children. The study's authors point out that the average high school graduate will likely spend 15,000 to 18,000 hours in front of a television but only 12,000 hours in school.

As television viewing time rises, time spent exercising outdoors declines, especially among girls. A decrease in physical activity seems to occur as girls move from the 11- to 13-year age group to the 14- to 16-year age group. African-American and Mexican-American children had lower rates of exercise, and higher rates of television viewing, compared with their white peers. The researchers found that 48% of black children watched 4 or more hours of television per day -- nearly double the national average.

The Journal of the American Medical Association (1998;279(12):938-942, 959-960)