TV Viewing, Childhood Obesity Linked
While the debate over television’s effects on kids focuses on what they watch, a new study of about 4,000 children underscores the importance of how much, showing that the more time they spend in front of the tube, the fatter they tend to be.
Moreover, the study firmly documents for the first time that black and Mexican American youths watch more TV than do whites, putting them at greater risk of obesity. Spending more than four hours a day in front of the TV were 43% of African American children, 30% of Mexican Americans, and 20% of non-Hispanic 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 TV and shirking exercise is 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’ fatness.
The new study’s results, made public today in the Journal of the American Medical Assn., “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% watched at least two hours a day, and 26% 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% more body fat than those who watched less than two hours.
Body fat was estimated from height and weight as well as by using calipers that measure the thickness of skin folds on the abdomen and back.
The number of children who are obese, meaning 30% above their ideal weight, grew by 7% 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, which contribute to heart disease, diabetes and other chronic diseases.
The findings strongly support the notion that the most important lifestyle factor in childhood obesity is television watching, Gortmaker said. “And that’s something that can be changed. Kids don’t have to watch TV 28 hours a week.”
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 children fatter: They rob kids of energy-burning exercise and encourage 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,” he added, perhaps taking a walk after dinner.
In some urban neighborhoods, concerns for safety may be a factor keeping kids and their families indoors, agreed Dr. Frederick James, chairman of pediatrics at Charles Drew University of Medicine and Science in Los Angeles. But, he added, there may also tend to be fewer recreational facilities and a dearth of adult supervision.
Some researchers say that the new study cannot definitively claim that watching TV caused the children’s weight problems. It may be that overweight kids just watch more TV than other kids, as Dr. Thomas Robinson of the Stanford Center for Research in Disease Prevention pointed out in an editorial in the AMA journal.
Andersen said the new study, which is based on an ongoing federal project called the National Health and Nutrition Examination Survey, does support the notion that watching TV contributes to childhood obesity. That is apparent from the directly proportional relationship between the amount of TV watched and the degree of body fat in many of the children tested.
Still, he and his coauthors said that final proof of the cause-and-effect relationship will come when researchers experiment directly with children and show that limiting TV cuts obesity rates.
In the meantime, he said, “Maybe we should worry less about the violence kids are exposed to on TV than the amount of time they spend watching it.”
