Study: Snacks Make Up 27% of Kids Calories

American kids snack three times a day and chips, candy and other junk foods now account for more than 27 percent of children's daily caloric intake, according to a new study released Tuesday.

The new research comes as childhood obesity is soaring in the U.S. with more than 12 million American children - roughly 17 percent - considered overweight.

The spike in snacking added 168 calories per day to kids' diets between 1977 and 2006, according to Carmen Piernas and Barry Popkin of the University of North Carolina reported.

"To put 168 extra calories per day in perspective: at 3,500 calories per pound, that translates to 17.5 extra pounds a year," says CBS News medical correspondent Dr. Jon LaPook.

The research appears in Health Affairs Journal, which also cites a study showing the national prevalence of obesity among U.S. children ages 10-17 has grown from 14.8 percent in 2003 to 16.4 percent in 2007.

First Lady Michele Obama has taken up the issue of childhood obesity. Earlier this month, Mrs. Obama invited a bipartisan group of lawmakers and Cabinet members to the White House Tuesday to help firm up plans for her national campaign against the growing problem.

The odds of obesity appear stacked against black and Hispanic children starting even before birth, another new study suggests.