Childhood Obesity Has Doubled in a Generation; Too Much TV, Too Little Activity Are to Blame, Study Shows

BUFFALO, N.Y. -- If there seem to be a lot more fat kids around than, say, 20 years ago, it is not an illusion, and it should come as no surprise that television-watching appears largely to blame.

A study in the current (March 15) issue of Archives of Pediatric and Adolescent Medicine, authored by a University at Buffalo epidemiologist, found that obesity among children between the ages of 8 and 16 has more than doubled in one generation.

The findings also showed that children who watched the most television were the fattest.

"There needs to be a national campaign to increase the opportunities for boys and girls to participate in lifetime physical activities," said Carlos Crespo, Dr.PH, UB associate professor of social and preventive medicine and first author of the study. "At the same time, we should have a national health objective of limiting children to two hours or less of television watching a day."

Crespo and colleagues from The Johns Hopkins University, the National Cancer Institute (NCI) and the Centers for Disease Control (CDC) analyzed data from 4,069 children who took part in the Third National Health and Nutrition Examination Survey conducted by the CDC between 1988 and 1994. Their study used data from this survey to assess the relationship between television watching, energy intake, physical activity and obesity.

The children received a physical exam and answered a number of questions about their lives, including how much and what kinds of food they ate during the previous 24 hours, how many hours of television they watched (obtained during two interviews) and how many times a week they were active enough to breathe hard or work up a sweat.

Analysis of data from this cross section of the nation's children revealed a number of statistics that have important public health implications, Crespo said. They are:

-- Nearly half of U.S. children between the ages of 8 and 16 watch more than two hours of television a day.

-- Sixty-five percent of black children and 53 percent of Mexican-American children watched more than three hours of TV a day, compared to 37 percent of white children. Seventeen percent of black children watched for five hours or more a day.

-- The prevalence of obesity increased as hours of TV watching increased.

-- The number of calories consumed increased as the number of hours of TV watching increased, and total calories were higher for boys than girls.

-- Only a little more than half of the children engaged in physical activity five or more days a week.

The results showed a closer association between television watching and obesity than between TV watching and physical activity, Crespo said, because it was hard for children to accurately recall how much exercise they took part in.

"If you ask how many hours they watch TV, they can do that quickly," Crespo said. "Physical activity is harder to quantify. Nevertheless, if they're watching TV, they aren't exercising."

Crespo said the lack of physical activity was particularly evident for girls between 14 and 16 years old, when less than one-third are active.

For many girls, particularly those living in marginal neighborhoods, he noted, the issue is safety. "Kids in 'bad' neighborhoods, especially girls, are told to go directly home from school and stay there," Crespo said. "Boys have more freedom to roam the neighborhood and can be more active. Many kids are home alone after school and with little else to do, they watch TV and they eat."

Results showed that girls who watched five or more hours of TV a day consumed 175 more calories daily than girls who watched one hour or less.

Also participating in the study were Ellen Smit, Ph.D.; Ross E. Anderson, Ph.D., and Susan J. Bartlett, Ph.D., of Johns Hopkins University; Richard P. Troiano, Ph.D., of the NCI, and Caroline A. Macera, Ph.D., of the CDC.

The study was supported in part by a grant from the National Institute on Aging.