Many Americans don't realize just how dangerous obesity can be, according to a new poll by The Associated Press-NORC Center for Public Affairs Research.

The study found that most people know extra weight can lead to heart disease and diabetes. But they don't realize it can also play a role in causing cancer, arthritis, sleep apnea, and infertility.

Jennifer Dimitriou, a bariatric dietitian at New York's Montefiore Medical Center, said many people are shocked when they discover obesity's far-reaching impact.

She said she hopes this discovery will motivate them to change their eating habits.

"Most people want to become healthier. It's the know-how, and understanding what the consequences are," Dimitriou said.

A third of U.S. children and teens and more than two-thirds of adults are obese or overweight.

The survey, conducted from Nov. 21 through Dec. 14, involved landline and cell phone interviews with with 1,011 adults nationwide. It has a sampling error of plus or minus 4.2 percentage points.