A study released on Monday found that the U.S. fast food industry is stepping up marketing efforts to target children starting as young as age two.

The study by Yale University's Rudd Center for Food Policy & Obesity was the largest ever on the marketing of fast foods to children. The report's authors studied marketing efforts of 12 of the nation's largest fast food chains, and examined the calories, fat, sugar and sodium in more than 3,000 kids' meal combinations and 2,781 menu items.

A major finding is that the U.S. youth exposure to fast food ads is dramatic. Children as young as age two are seeing more fast food ads than ever before. The average preschool child sees three ads for fast food every day. For teens the number is five.

In addition, the study shows that the amount of marketing of fast foods to children is going up. The fast food industry spent more than 4.2 billion U.S. dollars in 2009 on marketing and advertising on television, the Internet, social media sites and mobile applications. Much of the advertising is to create brand loyalty as much as it is to promote certain foods.

Restaurants rarely offer parents the healthy kids' meal choices, according to the study. Only 12 of 3,039 possible kids' meal combinations meet nutrition criteria for preschoolers. Only 15 meet nutrition criteria for older children.

"Despite pledges to improve their marketing practices, fast food companies seem to be stepping up their efforts to target kids, " said lead researcher Dr. Jennifer L. Harris, director of marketing initiatives at the Rudd Center.

Experts called on fast food companies to drastically reduce the total amount of marketing that children and teens see for fast food and the iconic brands that sell it to fulfill their responsibility as partners in public health.

VietNamNet/Xinhuanet