WASHINGTON—One-third of American adults are obese, according to new U.S. government figures released Wednesday, but the rate of increase seen in recent decades has slowed.

Figures from the National Center for Health Statistics showed 34% of American adults age 20 and older were obese in 2007-08 while 68% were considered overweight or obese. In children ages 2 through 19, 17% were considered obese while 32% were considered overweight. Broadly, the figures are similar to rates seen in 1999-2000.

"Obesity...