The amount of TV preschoolers watch seems to contribute to what their waist size and athletic abilities will be when they reach fourth grade, researchers report.
The study, from researchers at the University of Montreal and Sainte-Justine Mother and Child University Hospital in Canada, found that every hour of TV children ages 2½ to 4½ watched not only added to their waistline but also affected their ability to perform in sports.
"We already knew that there is an association between preschool television exposure and the body fat of fourth-grade children, but this is the first study to describe more precisely what that association represents," study senior author Dr. Linda Pagani said in a university news release.
In conducting the study, the researchers asked the parents of more than 1,300 children ages 2½ to 4½ about their preschoolers' weekly TV habits. They also measured the children's waists and had the kids perform a standing long jump to assess their muscular fitness level.
The study authors noted that the standing long jump test is useful in assessing athletic ability because many sports, including football, skating and basketball, require similar "explosive leg strength."
The investigators found that the children watched an average of nearly nine hours of TV each week when they were 2½ years old. By the time the children were 4½, they were watching an average of nearly 15 hours of TV each week.
The findings revealed that each hour of TV 2½-year-olds watched per week was consistent with a reduction of about one-third of a centimeter (0.13 inches) in the distance they were able to jump.
"The pursuit of sports by children depends in part on their perceived athletic competence," the study's lead author, Dr. Caroline Fitzpatrick, said in the news release. "Behavioral dispositions can become entrenched during childhood, as it is a critical period for the development of habits and preferred activities. Accordingly, the ability to perform well during childhood may promote participation in sporting activities in adulthood."
By the time the kids were 4½, their waist size increased by about half a millimeter (0.019 inches) for every hour of TV they watched above their weekly TV habit at the age of 2½. This means that a child who watched 18 hours of TV weekly at the age of 4½ would have an extra 7.6 millimeters (0.3 inches) on their waistline by the time they are 10 years old.
Although more research is needed regarding the effects of TV viewing on children's health, the study authors concluded that policymakers should focus on the environmental factors linked to childhood obesity.
"The bottom line is that watching too much television -- beyond the recommended amounts -- is not good," Pagani said. "There have been dramatic increases in unhealthy weight for both children and adults in recent decades. Our standard of living has also changed in favor of more easily prepared, calorie-dense foods and sedentary practices. Watching more television not only displaces other forms of educational and active leisurely pursuits but also places them at risk of learning inaccurate information about proper eating."
Although the study uncovered an association between TV viewing and waist size and fitness levels, it did not prove a cause-and-effect relationship.
Pagani added, however, that, "These findings support clinical suspicions that more screen time in general contributes to the rise in excess weight in our population, thus providing essential clues for effective approaches to its eradication."
The study was published in the July 15 issue of the International Journal of Behavioral Nutrition and Physical Activity.