Ads for unhealthy foods may explain link between television viewing and overweight in children

Boston, MA -- Researchers from the Harvard School of Public Health (HSPH) and Children's Hospital Boston found that kids who spend more time watching television also eat more of the calorie-dense, low-nutrient foods advertised on television. Previous studies had demonstrated that children who watch more television are more likely to be overweight, but this is the first time a research team has found evidence for a mechanism explaining that relationship. The study results appear in the April 2006 issue of the Archives of Pediatric and Adolescent Medicine.

"We've known for a long time that television viewing is a risk factor for overweight, though the common perception is that this is due to the fact that it's a sedentary use of time," said Jean Wiecha, the study's lead author and a senior research scientist at HSPH. "This study provides evidence that television is effective in getting kids to eat the foods that are advertised, and this drives up their total calorie intake."

Wiecha and her colleagues collected baseline data on dietary patterns and television viewing habits for 548 Boston-area students in sixth and seventh grade and then repeated these measurements 19 months later. When surveying the students about their food intake, the researchers asked specifically about snacks and beverages commonly advertised on television, such as soda, chips, fast food and baked snacks like cookies. Students were also asked to estimate the number of hours spent watching television each day of the week.

The results of the study showed that each hour of increased television viewing over baseline was associated with a total energy increase of 167 calories -- just about the amount of calories in a soda or a handful of snack food, said Wiecha. Each additional hour of television viewing was also independently associated with increased consumption of foods commonly advertised on television, and these foods were shown to be responsible for much of the calorie increase. Viewing time seemed to have the strongest connection to additional consumption of sugar-sweetened beverages.

Twice as many children and almost three times as many teens are overweight today compared to their counterparts growing up 20 years ago. Overweight young people are more likely to become overweight or obese adults who are at risk for diseases like diabetes and heart disease. The results of this study bolster a longstanding recommendation by the American Academy of Pediatrics to limit children to less than two hours of television each day to both lessen sedentary time (a risk factor for childhood overweight) and reduce exposure to content associated with negative consequences.

While further research on this topic is necessary, particularly on the "dosage" of advertising necessary to influence dietary choices, Wiecha believes that her team's results have important implications for parents and the food advertising industry. "Basically, we concluded that kids in this study eat what they watch," she said. "This should help inform discussions about food marketing aimed at children."

This research was funded by grants from the National Institute of Child Health and Human Development, the National Institute of Diabetes and Digestive and Kidney Diseases, the Centers for Disease Control and Prevention and the Charles H. Hood Foundation.

Harvard School of Public Health is dedicated to advancing the public's health through learning, discovery, and communication. More than 300 faculty members are engaged in teaching and training the 900-plus student body in a broad spectrum of disciplines crucial to the health and well being of individuals and populations around the world. Programs and projects range from the molecular biology of AIDS vaccines to the epidemiology of cancer; from risk analysis to violence prevention; from maternal and children's health to quality of care measurement; from health care management to international health and human rights.

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