With their large portion sizes and high grease loads, restaurant meals are generally less nutritious than their home-cooked counterparts. But how bad are they, particularly for young people?

When teenagers ate food away from home, found a new study, they consumed as much as 300 extra calories a day or more. Kids and teens also took in more sugar, salt, saturated fat and total fat when they visited restaurants than when they ate at home.

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The study included data on more than 4,700 young people, ages 2 through 19, who were surveyed about their eating patterns between 2003 and 2008.

When they ate at fast-food restaurants, kids up to age 11 ate an extra 125 calories over the course of a day, while adolescents age 12 and older ate about 310 excess calories, the researchers report today in the journal Archives of Pediatrics & Adolescent Medicine. Even when they ate at full-service restaurants, kids added 160 calories to their daily consumption while teens added about 270.

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In the older group, eating at fast-food restaurants led teens to consume 13 percent more sugar, 22 percent more total fat, 25 percent more total fat and 17 percent more sodium.

Kids who ate out more drank more sodas and other sugar-sweetened drinks. And the difference in calories and fat consumed was greatest for kids from lower-income and minority families.

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The findings should add weight to public policies that reduce the amount of food kids eat from restaurants and fast-food joints, the authors say. Those might include zoning rules that restrict restaurants near schools, or regulations that reduce portion sizes or limit food marketing to kids.

"Fast-food advertising on television is the most frequently seen category of food-related product advertisements by children and teens, exposure has trended upward substantially, and greater exposure has been associated with higher frequency of consumption and higher body weight," wrote the authors, from the University of Illinois at Chicago.

"Only two fast-food companies are members of the self-regulatory Children's Food and Beverage Advertising Initiative and, despite this initiative, the poor nutritional content of fast-food advertising has been well documented. Further consideration should be given to improve the initiative's nutritional guidelines and to apply it to adolescents."

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