WEDNESDAY, Feb. 28, 2007 (HealthDay News) -- The more time 3-year-olds spend glued to the television, the worse their diet will be, a new study reveals.
The link between TV watching and a poor diet was evident on a per-hour basis, with each additional hour of viewing translating into more consumption of calories, sugar, fast food and trans fats, and less consumption of fruits, vegetables, calcium and dietary fiber.
"The obesity epidemic has not even spared our youngest children," cautioned study author Sonia A. Miller, an undergraduate at Harvard Medical School. She believes that "reducing screen time among young children seems to be important" in preventing the early development of poor eating habits and obesity among toddlers.
The findings were expected to be discussed Wednesday at the American Heart Association's Annual Conference on Cardiovascular Disease Epidemiology and Prevention, in Orlando, Fla.
Miller's team noted the American Academy of Pediatrics (AAP) currently recommends that children under the age of 2 not be exposed to TV at all, while youngsters over the age of 2 be limited to no more than two hours of TV per day.
To assess how well real-world practice matches that ideal, the Harvard group analyzed questionnaires completed by mothers of more than 1,200 children. All of the children were enrolled at birth in a Massachusetts nutrition study funded by the U.S. National Institutes of Health (NIH).
The surveys gathered information on both the weekday and weekend TV-viewing habits of boys and girls in the month prior to the study launch. Information on dietary intake in that period was also compiled for all the children, who averaged just over 3.
Almost three-quarters of the children were white, and 87 percent came from families earning more than $40,000 per year. Nearly three-quarters of the mothers had obtained at least a college degree.
The authors found that, on average, the kids watched 1.7 hours of TV daily -- a figure falling within AAP guidelines.
However, for those children who watched greater amounts of TV, every added hour of viewing was associated with deficits in the healthiness of their diet.
Overall food consumption increased by just over 46 calories a day with each additional hour of TV viewing, the researchers reported. That may not seem like much, but prior research suggests that all the excess weight gained by American adolescents over the past decade stems from just an extra 150 calories per day.
So, nearly one-third of this weight gain might be linked to that single extra hour of TV or video games per day, the researchers said.
A one-hour bump in TV viewing was also associated with the consumption of an additional serving of a sugar-sweetened beverage (including juice) per week; an additional 0.3 serving of fast food per month; and an additional 0.06 serving of red and processed meat per day, the team found.
The percentage of daily calories constituted by trans fats also rose with increased exposure to TV.
At the same time, kids' consumption of healthy foods dropped as TV viewing rose. A one-hour rise in TV viewing was linked to a drop in vegetable intake of 0.2 servings per day; a dietary fiber drop of 0.4 grams per day; and a decline in calcium intake of 23.2 milligrams per day, the researchers reported.
Miller's group could not determine whether (or how) TV viewing provokes children to switch from healthy foods to unhealthy ones.
Excess TV time may increase health risks -- such as obesity and cardiovascular complications -- through the promotion of poor eating habits, rather by acting as a substitute for physical activity, the researchers said. TV could also boost unhealthy eating via kids' exposure to certain television commercials (for sugary or fatty foods) or by encouraging kids to snack while watching television, they theorized.
"We hope that our results may provide clinicians, parents and policy makers with an understanding for why screen time should be limited among young children," Miller said.
Dr. Rebecca Unger, an attending pediatrician at Children's Memorial Hospital and a clinical associate professor of pediatrics at Northwestern University in Chicago, said the findings make sense.
"There have been other studies that have shown that increased TV watching correlates with higher obesity in kids," she said. "They've underlined a lot of reasons why we need to limit TV. This is another one."
"When I see kids who are overweight, a lot of the time there's really excessive TV watching going on," added Unger. "And this is showing, the more hours, the more unhealthy the pattern is. It's not that kids can't watch TV. We just need to keep it in check."
For more on pediatric obesity, visit the American Academy of Pediatrics.