Nearly 40 percent of children in Georgia are overweight or obese -- the third-highest rate in the country -- while adults in South Carolina rank fifth in obesity, according to data released Wednesday.

Many of those heavy kids, particularly boys, are already developing heart changes that will haunt them the rest of their lives and could signal a grim future for an entire generation, researchers said.

According to a report from Trust for America's Health and the Robert Wood Johnson Foundation, 37.3 percent of Georgia children ages 10-17 are obese or overweight. In South Carolina the rate is 33.7 percent, 13th highest among the states.

About one-third of adults in the Palmetto State -- 29.7 percent -- are obese, while Georgia adults are not far behind at 27.9 percent, the 14th-worst rate in the country. Mississippi was highest for both children and adults, at 44.4 percent and 32.5 percent, respectively. Colorado, at 18.9 percent, was the only state that did not have at least 20 percent obesity among adults.

"To keep this in perspective, back in 1991, not a single state had an obesity rate above 20 percent," said Jeff Levi, executive director of the Trust for America's Health. "So there's been a dramatic change in the country in a relatively short period of time."

There was good news of a sort in the rankings -- 23 states reported an increase in adult obesity this year, down from 37 states a year ago, said James Marks, senior vice president of the Robert Wood Johnson Foundation. And many states and communities are taking action, either by tightening controls on what is served in schools or encouraging physical activity, he said.

"We are not confident that the states that have acted so far have done enough to reverse the epidemic in their children," Dr. Marks said. "We in fact suspect that more will have to be done."

Both House and Senate versions of health care reform bills provide for "meaningful expansion of such community prevention and wellness programs," Dr. Levi said. "Both the House and the Senate bills mandate a national prevention strategy, and obesity prevention would be a central part of these strategies."

Obesity accounts for a quarter of skyrocketing health care costs, and it adds billions to the nation's bill, Dr. Levi said.

But the worst may lie ahead.

"We have a huge wave of obese children, obese young adults, obese older adults coming whose costs will be part of what bankrupts us as a nation unless we can get them to be healthier now," Dr. Marks said.

For some, that may already be too late. The Georgia Prevention Institute at the Medical College of Georgia has done some of the most comprehensive studies on the impact of obesity and heavy weight in children. Ten or 15 years ago, the institute's researchers looked for the precursors of adult diseases such as hypertension and type II diabetes in children, said Director Gregory Harshfield.

"We now look at these same diseases the adults have in kids," he said. "Kids have hypertension, which they didn't have before. Kids have type II diabetes, which they didn't have before."

Particularly troubling is what is happening in overweight or obese boys as young as 15. The fat cells are causing the adrenal gland to secrete a hormone called aldosterone that triggers a cascade that leads to higher blood pressure and even physical changes in the heart, causing it to become enlarged, Dr. Harshfield said.

"Once you get a bigger heart, you've got problems all the way down the line," he said. "Their physiology is being changed dramatically. When these kids are 40, they are going to look like a 60-year-old in their cardiovascular systems" because of the strain.

Those who study these diseases in adults need to start talking to pediatricians and vice versa, and researchers need to better understand the mechanisms to come up with treatment, Dr. Harshfield said. That's because the problem doesn't seem to be going away.

"If we're not going to stop it, we better know how to treat it," he said.