Written By Michelle Healy, USA TODAY
Here's some practical advice to parents who are concerned about their children's weight: Serve them meals on smaller plates, pay attention to what they watch on TV, and make sure they get adequate sleep at night.
These suggestions are based on three new studies in April's Pediatrics, released online today.
Nationally, about a third of kids and adolescents ages 2 to 19 are obese or overweight, government statistics show. Children are classified as overweight or obese based on where they fall on body mass index (BMI) charts, a measure based on height and weight.
In a study of 41 first-graders, researchers found that when given large, adult-size dinner plates and bowls, students served themselves larger portions of food and consumed almost 50% of the extra calories they put on their plates.
On average, 80% of the kids served themselves 90 calories more at lunch when using adult-sized dinner plates than when using child-sized plates (roughly the size of an adult salad plate). And when the kids said they liked the meal, they served themselves an average of 104.2 calories more.
Although the kids served themselves more of the fruit side dish, they did not take a larger portion of the vegetable side dish.
"We know large portions have a pretty consistent effect in making kids eat more than they would if the portion sizes were smaller, says study co-author Jennifer Orlet Fisher, an associate professor of public health at Temple University in Philadelphia.
"It really seems that offering kids smaller plates could actually be potentially helpful in keeping portion size in check and maybe appetite in check," she says.
In a paper examining the relationship between different types of "screen" media and increased BMI among young adolescents, researchers find that not all devices have the same effect and that television use appears more problematic.
They compared data collected from 91 teens, ages 13 to 15, about TV viewing, computer use and video game playing, including the amount of time and the level of attention given to the devices and compared it with BMI scores.
Data about the teens' screen media habits came from time-use diaries in which they recorded their activities, and personal digital assistants that randomly pinged them during non-school hours requesting details about their media use.
According to the analysis, there was a clear association between teens who paid primary attention to television and having a higher BMI, says study co-author, Michael Rich, director of the Center on Media and Child Health at Boston Children's Hospital. That association was was not true for computer use or video-game playing, nor was increased BMI associated with the overall amount of time spent watching TV, he says.
"It's those kids who told us, 'My primary attention was paid to television,' even if they say it was done while doing homework or texting," says Rich, a pediatrician. "They were the ones that had the most robust relationship with increased BMI."
As has been suggested in other studies, the potential culprit may be the attention paid to TV commercials, Rich says. "TV, unlike the other screen media, is supported by advertising, and much of it is for high-calorie, nutritionally questionable snack foods. Advertising works best when you pay attention to it," he adds.
The new sleep study is the latest in a growing body of research to suggest that insufficient sleep may contribute to the rise in adolescent obesity. It has been proposed that sleep deprivation is related to increased BMI because it increases levels of a hunger hormone and decreases levels of a fullness hormone, which could lead to overeating and weight gain.
Using data collected every six months over four years from 1,390 high school students (grades 9 through 12), the study is one of the longest yet based on repeated measures of a high school population, says lead study author Jonathan Mitchell, a postdoctoral fellow in biostatistics and epidemiology at the University of Pennsylvania in Philadelphia.
Based on the study's results, researchers predict that increasing sleep from 7.5 hours per day (the average in the study) to the medically recommended 10 hours per day could reduce the proportion of teens with a BMI at or above 25 (classified as overweight) by 3% at age 14 and by 4% to 6% at age 18.
"It's a prediction, not conclusive data, but the findings point to the potential public health benefits that increasing sleep duration could have for overweight and obese adolescents in the U.S.," says Mitchell.