SAN DIEGO – Watching at least 1 hour of television daily was associated with increased likelihood of overweight and obesity in kindergartners and first graders in a large national longitudinal study.
The American Academy of Pediatrics recommends that children watch less than 2 hours of TV daily, but this new analysis indicates that watching at least 1 hour but less than 2 hours is associated with unhealthy weight gain, Dr. Mark D. DeBoer said at the annual meeting of the Pediatric Academic Societies.
Bruce Jancin/Frontline Medical News
Dr. Mark D. DeBoer
“The AAP may wish to consider reducing the recommended limits of TV viewing, with an emphasis on replacing this time with physical activities and learning opportunities,” declared Dr. DeBoer, a pediatrician at the University of Virginia, Charlottesville.
He and his coinvestigators analyzed data on 12,389 young children participating in the nationally representative Early Childhood Longitudinal Study-Kindergarten Cohort 2011. The study collected parentally reported hours and minutes of weekly daytime TV watching and determined body mass index z scores when the children were in kindergarten and again a year later as first graders.
As kindergartners, participants averaged 2.0 hours of TV per day, with 33% of the children exceeding the AAP-recommended 2-hour limit. As first graders, they averaged 1.6 hours of TV daily, and 15.7% of them exceeded 2 hours; however, when the first graders’ computer screen time was added in, 36.7% of them exceeded the AAP recommendation.
In a logistic regression analysis adjusted for race/ethnicity, gender, socioeconomic status, and amount of computer use, kindergartners who watched at least 1 hour and less than 2 hours of TV daily were 43% more likely to be overweight and 47% more likely to be obese than their peers who watched less than 1 hour. Moreover, kindergartners who watched 2 or more hours of TV per day were 58% and 75% more likely to be overweight and obese, respectively, than those who watched less than 1 hour.
A similar cross-sectional analysis conducted during first grade showed much the same: Children who watched at least 1 but less than 2 hours of TV daily were 40% more likely to be overweight and 48% more likely to be obese than those watching less than 1 hour per day. Children who watched at least 2 hours of TV daily were 53% and 61% more likely to be overweight and obese, respectively.
Dr. DeBoer and coworkers also conducted a longitudinal analysis examining the relationship between TV time and change in BMI z scores over the course of 1 year of follow-up from kindergarten and first grade. The group watching less than 1 hour of TV per day showed a slight decrease in BMI z score during the year, while those watching 1 to less than 2 hours had a mean 0.16-point increase in z score, which translates into roughly a 0.3-kg weight gain for an average-height child in this age group.
Computer use and video game time had no association with weight status.
The mechanism for the relationship between TV viewing and weight gain in children is believed to involve the sedentary nature of the activity along with exposure to advertisements for snack foods.
Several audience members rose to take issue with Dr. DeBoer’s call for the AAP to lower its recommended maximum amount of TV viewing.
“You’ve described an association,” one pediatrician said. “It isn’t necessarily the case that if you reduce the TV time, you reduce obesity in these individuals.”
Dr. DeBoer agreed that the observed association “may or may not be causal,” but he noted further, “There have been some studies that targeted reducing TV viewing that have shown favorable effects on BMI over time, so that is supportive.”
The Early Childhood Longitudinal Study-Kindergarten Cohort 2011 is funded by the U.S. Department of Education’s National Center for Education Statistics. The TV time/body weight analysis was funded by the Doris Duke Foundation. Dr. DeBoer reported having no financial conflicts.