Obese Americans spend about 42 percent more on health care than normal-weight Americans, according to a new study based on 2006 figures.

Medical spending on obesity-related conditions is estimated to have reached $147 billion a year in 2008, according to the new study, published online on Monday in the journal Health Affairs. That figure represents almost 10 percent of all medical spending, the study found.

Obese Americans spend about $1,429 more on health care each year than the roughly $3,400 spent by normal-weight Americans.

Most of the excess spending is for prescription drugs needed to manage obesity-related conditions, said Eric A. Finkelstein, one of the study’s authors and the director of the public health economics program at the Research Triangle Institute, a nonprofit research organization.

The results were presented on Monday at the first Weight of the Nation conference, which was held in Washington by officials at the Centers for Disease Control and Prevention.

“Obesity, and with it diabetes, are the only major health problems that are getting worse in this country, and they’re getting worse rapidly,” Dr. Thomas R. Frieden, director of the C.D.C., said.

The average American consumes 250 more calories per day than just two decades ago, Dr. Frieden noted, and the rising obesity rate is the single greatest contributor to a national epidemic of diabetes.