While the debate over television’s effects on kids focuses on what they watch, a new study of some 4,000 children underscores the importance of how much they watch, showing that the more time they spend in front of the tube, the fatter they tend to be.
The study also firmly documents for the first time that black and Latino youths watch more television than do whites, putting them at greater risk of obesity. Spending more than four hours a day watching television were 43 percent of black kids and 30 percent of Mexican Americans but only 20 percent of non-Latino whites.
One reason for the ethnic and racial differences in viewing trends, researchers speculate, is that parents in urban neighborhoods may discourage their children from playing outside because of crime. Thus, the fear of crime appears to contribute to the “epidemic of obesity,” researchers say.
Though it may seem obvious that watching television and shirking exercise are behind the childhood obesity epidemic, researchers have had surprising difficulty nailing down those factors, with some previous studies showing no correlation between TV viewing habits and kids’ obesity.
The new study’s results, made public today in the Journal of the American Medical Association, “are consistent, make sense, and indicate a serious problem in the United States,” said Steven Gortmaker, a sociologist at the Harvard School of Public Health who has studied TV viewing and obesity.
In the most comprehensive study of its kind, the researchers analyzed data from lifestyle interviews with 4,063 children between 1988 and 1994. Consistent with previous surveys, the study found high rates of TV viewing overall: 67 percent watched at least two hours a day, and 26 percent racked up four or more hours.
The central finding was that kids who watched a lot of TV were measurably fatter than those who watched relatively little. For instance, children who watched at least four hours daily had about 20 percent more body fat than kids who watched fewer than two hours.
The number of kids who are obese, meaning 30 percent above their ideal weight, grew by 7 percent from the early 1980s to the early 1990s, according to federal survey data. That trend is troubling, public health experts say, because childhood obesity is often a harbinger of serious weight problems in adulthood.
The findings strongly support the notion that the most important lifestyle factor in childhood obesity is television watching, Gortmaker said.
The study’s lead author, Ross Andersen, an exercise physiologist at Johns Hopkins School of Medicine, said long bouts of TV have two ways of making kids fatter: It robs kids of energy-burning exercise and encourages high-calorie snacking.
“We’re not slamming TV watching, because it can be a nice family pastime,” said Andersen, who collaborated with researchers at the National Heart Lung and Blood Institute and the Centers for Disease Control and Prevention. “But families should look for more ways they can be physically active together,” perhaps taking a walk after dinner.