Childhood obesity is threatening the health of one-third of the nation's young people. Nearly 25 million children age 17 and younger are considered obese or overweight, costing $14 billion a year in medical expenses, the foundation said.
"These children live sicker and are likely to die younger if our nation continues to have this problem with childhood obesity," Dr. Risa Lavizzo-Mourey, the president and CEO of the foundation, told CBS News.
To halt a trend building over the past four decades, the foundation is offering to fund programs that focus on improving access to affordable healthy foods or on how to increase physical activity in schools and communities.
"We know that we are going to need to use this to help families have safer places for kids to play and get exercise, and get back to being active," Lavizzo-Mourey said. "What we hope to do with this money is pull people from all across the country, galvanize them, to work together to reverse this epidemic."
A glut of cheap junk food and convenience — fewer of today's kids walk to school or need to get up to change the television channel — have obscured the facts of the "energy balance," Lavizzo-Mourey said.
Simply put, people are eating more energy than they burn, she said.
"We are eating more of our meals in restaurants. It's harder to control healthy choices when you're eating out," Lavizzo-Mourey said. "A lot of these things happened over many years, and so slowly it was hard to see it was happening."
The foundation believes the $500 million is the largest amount ever directed against childhood obesity. It comes atop $80 million spent on the topic by the foundation over the past three years, Lavizzo-Mourey said.
"Childhood obesity affects all of us — every race and ethnic group, all income levels and every area of the country," the foundation says on its Web site. "It's going to take all of us — government, schools, food and beverage companies, health care providers, families and other foundations — to turn the tide."
Former U.S. Surgeon General Dr. David Satcher called the foundation's effort "tremendous." The "investment highlights just how critical this problem has become and is a call to all the nation that past efforts have been too small, too slow and too fragmented," Satcher said in a statement provided by the foundation.
The foundation also is the largest funder of the Alliance for a Healthier Generation, a project of the William J. Clinton Foundation and the American Heart Association, whose efforts include having schools serve healthier food.
The Robert Wood Johnson Foundation's new initiative will build on successful programs, such as Arkansas' trendsetting efforts that included sending home obesity report cards to warn parents of overweight kids' health risks.
Without action, health costs will spiral as sick children become ailing adults, according to the foundation, the nation's largest philanthropy devoted exclusively to improving the health of all Americans.
"The epidemic of obesity in children is causing kids to have adult diseases. And those adult diseases have serious consequences, and give the potential for having a sicker adulthood and shorter life," Lavizzo-Mourey said.
Children who develop diabetes in their teens or early 20s are more likely to suffer associated ailments such as kidney failure, heart trouble and amputation by middle age, she said. Heavier children also have increased rates of asthma, high blood pressure and arthritis.
"And the psychological impact on kids cannot be discounted. These kids get more bullying," she added.
In 1963, the average 10-year-old girl weighed 77 pounds; now she weighs about 88. A 10-year-old boy who was 74 pounds then is now about 85 pounds, according to the foundation.
The foundation wants to pay for projects that have the potential of being done on a broad scale and meshing with other efforts. It will emphasize efforts to reach children facing the greatest risk for obesity and related health problems: poor blacks, Hispanics, Native Americans, Asian Americans and Pacific Islanders.
These could include low-tech solutions such as the "walking school bus," where parents go house-to-house, gathering children and escorting them to school, giving them exercise as well as instruction on how to cross the street, Lavizzo-Mourey said.
The foundation hopes promote ideas that prompt grocery stores to stock more healthy foods by creating interest in such food, she said.
Other efforts could focus on teaching adults and children about healthy eating, including how many hours of play it takes to burn off a number of calories, Lavizzo-Mourey said.
She added, "Parents who want to raise healthy kids see they almost have insurmountable barriers to provide that kind of life for their kids."