The New York Times reported, in an April 2007 article, that the Robert Wood Johnson Foundation plans to spend more than $500 million over the next five years to reverse the increase in childhood obesity nationally, including Texas. It is one of the largest public health initiatives ever tried by a private philanthropy.

"This is an epidemic that is going to cost the country in terms of morbidity and mortality and economically," said Dr. Risa Lavizzo-Mourey, the foundation's president and chief executive. "The younger generation is going to live sicker and die younger than their parents because of obesity."

The foundation estimates that roughly 25 million children 17 and under are obese or overweight, nearly a third of the 74 million in that age group, according to Census Bureau data and a 2006 study published in The Journal of the American Medical Association.

Many of those children are poor and live in neighborhoods where outdoor play is unsafe and access to fresh fruits and vegetables is limited. "In many cases, the environment makes it almost impossible for them to choose healthy lifestyles," Dr. Lavizzo-Mourey said. "We're going to try to change that."

The foundation plans to invest in programs to improve access to healthy food, encourage the development of safe play spaces, increase research to enhance understanding of obesity and prod governments into adopting policies to address the problem, among other things.

Experts on childhood obesity welcomed the foundation's plans.

"Government grants for biomedical research in general, including obesity research, are being funded at the lowest levels I've seen in my career," said Dr. David Ludwig, director of the Optimal Weight for Life Clinic at Children's Hospital Boston and author of a new book, "Ending the Food Fight." "So we are especially dependent on philanthropic support."

Philanthropy has long fueled improvements in health, from John D. Rockefeller, whose money produced a yellow fever vaccine, to Bill and Melinda Gates, who are underwriting new health technologies and vaccines to address a variety of global problems.

Robert Wood Johnson, who built Johnson & Johnson into one of the world's largest health and medical care products companies, established his foundation at his death in 1968 with 10,204,377 shares of the company's stock. He committed it to improving the health of Americans.

The foundation played a major role in curbing tobacco use in this country, spending $446 million from 1991 to 2003 toward that goal, and it plans to use those experiences to shape its attack on childhood fat.

Since 1995, the number of adult and teenage smokers has declined 12.6 percent and 18 percent, respectively.

"It was a very carefully thought-out strategic initiative," said Joel L. Fleishman, a professor of law and public policy at Duke University. The foundation underwrote research, prevention and smoking-cessation programs, and increased awareness of smoking's dangers.

Over the last few years, the foundation has pledged $80 million to childhood obesity programs, like grants to the Food Trust to persuade supermarket operators to return to poor neighborhoods.

Its new effort intends to capitalize on and enhance efforts by the food industry and school districts and governments to address the problem, Dr. Lavizzo-Mourey said. Several snack food producers are making changes in their packaging and ingredients, and three soft-drink companies said they would no longer supply sweetened drinks to school cafeterias and vending machines.

Several states have mandated changes in school menus, increased physical education requirements and begun reporting students' body mass index scores to parents.

In Arkansas, which has one of the most comprehensive programs aimed at the problem, obesity among the 450,000 children in 1,300 public schools has plateaued.

Obesity is a growing American epidemic that takes root early in life. It imposes a variety of health risks that can appear at any phase in life. As you'll discover, what affects your health also will eventually affect your bank account.