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(CNN) -- Tom Hanks has revealed that he has been diagnosed with Type 2 diabetes.

During an appearance Monday night on "Late Show With David Letterman" to promote his new film "Captain Phillips," the actor said his physician told him he had moved from a prediabetic state to having the disease.

"I went to the doctor and he said, 'You know those high blood sugar numbers you've been dealing with since you were 36? Well, you've graduated,' " Hanks told Letterman. " 'You've got Type 2 diabetes, young man.' "

With diabetes, a person's blood sugar is not well-regulated, and the body either does not produce enough insulin to function properly or the cells in the body do not react to the insulin present.

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Hanks is one of several celebrities, including Paula Deen and Sherri Sheppard, who have gone public with having diabetes. Weight is often a factor in the disease, and while Hanks appeared fit on "Letterman," his weight has fluctuated over the years for various roles.

In 1992 he reportedly gained 30 pounds to play coach Jimmy Dugan in "A League of Their Own." He told Entertainment Weekly in 2000 that he lost more than 50 pounds for his role in the film "Cast Away."

The "Forrest Gump" star said his condition is manageable through diet, and Letterman said that he too has high blood sugar. Hanks joked that he can't follow his doctor's advice to return to his high school weight to help control his diabetes.

"And I said to (the doctor), 'Well I'm gonna have Type 2 diabetes,' " Hanks joked. "Because there is no way I was gonna weigh what I weighed in high school. ... I weighed 96 pounds in high school."

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