NEW YORK, July 28 (RIA Novosti) - Medical spending in the U.S. due to obesity has doubled in the past 10 years, and may now have reached around $147 billion per year, a new study has found.

From 1998 and 2006, the national obesity rate increased by 37 percent, according to a study conducted jointly by the RTI International research institute, the Agency for Healthcare Research and Quality, and the U.S. Centers for Disease Control and Prevention.

Health problems resulting for obesity are responsible for 9.1 percent of annual medical expenditure, up from 6.5 percent in 1998. An average obese person incurs 42 percent more medical costs than a person of normal weight.

The costs are due almost entirely to diseases caused by obesity rather than prevention of obesity itself.

"Although bariatric surgery and other treatments for obesity are increasing in popularity, in actuality these treatments remain rare," said Eric Finkelstein, Ph.D., the study's lead author.

"As a result, the medical costs attributable to obesity are almost entirely a result of costs generated from treating the diseases that obesity promotes. Thus, obesity will continue to impose a significant burden on the health care system as long as the prevalence of obesity remains high," Finkelstein said.