Harris and colleagues spent a year studying 12 big fast-food chains, analyzed the calories, fat, sugar and sodium in menu items and kids' meal combinations, and studied what children and teens ordered.
The report, available at www.fastfoodmarketing.org, finds the industry spent more than $4.2 billion in 2009 on marketing and advertising on television, the Internet, social media sites and mobile applications.
"Today, preschoolers see 21 percent more fast food ads on TV than they saw in 2003, and somewhat older children see 34 percent more."
McDonald's Corp has 13 websites, attracting 365,000 unique child visitors under 12 every month. One, ronald.com, specifically targets preschoolers.
The U.S. Centers for Disease Control and Prevention says two-thirds of American adults and 15 percent of children are overweight or obese. In some states, the childhood obesity rate is above 30 percent.