New research shows that obesity and the cost of treating obesity-related illnesses in the United States rose dramatically between 1998 and 2006.

The study was published Monday in the journal Health Affairs. It said obesity-related health spending was estimated at $147 billion a year in 2006, roughly double the $74 billion estimated just eight years earlier.

Researchers from a nonprofit group, the Research Triangle Institute, and the U.S. Centers for Disease Control and Prevention said in their study that obesity-related health conditions, including diabetes and heart disease, now account for 9.1 percent of all medical spending.  That's up from 6.5 percent in 1998.

The report says obesity itself rose 37 percent in that time, and nearly a third of Americans are now considered to be obese.

The CDC says the United States must bring down its obesity rates to reduce health care costs.  It recommends that communities fight obesity by promoting healthy eating and physical activity.

The study also was released at the Weight of the Nation CDC conference in Washington on health and obesity.

Some information for this report was provided byAP and Reuters.