The nation's obesity related health bills may cost twice as much as previously thought, according to a new study by John Cawley of Cornell University and Chad Meyerhoefer of Lehigh University. The report was released this week by the National Bureau of Economic Research, a nonprofit, nonpartisan research organization.

Today, nearly 17 percent or $168 billion of U.S. medical costs can be blamed on obesity. Other studies only estimated about 9 percent or $147 million.

One study last year estimated that obesity added only about $1,400 to a person's annual medical bills. But experts say it now costs more than $2,800 a year to treat obesity.

Researchers say past studies have underestimated the impact on medical spending.

"I think these are the most recent and perhaps statistically sound estimates that have come out to date," said Kenneth Thorpe, a health policy researcher at Emory University who has focused on the cost of health care.

The study's authors at first were a bit surprised by how large their estimates were. But obesity is clearly a major burden on society, said Cawley, an associate professor of policy analysis and management.

"It's hard to find conditions that aren't worsened or made more expensive by obesity," he said.

The study was based on a federal survey of 24,000 non-elderly adult patients from the years 2000 through 2005.