By Margaret Farley Steele and Steven Reinberg, HealthDay Reporters

Tom Hanks, the Academy Award-winning actor, revealed back in 2013 that he had joined millions of Americans in a new role -- that of type 2 diabetic.

Hanks, 57, was discussing his latest film on CBS' "The Late Show With David Letterman" when he made the announcement.

"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. You've got type 2 diabetes, young man,'" Hanks said.

Over the years, the actor's weight has bounced up and down like Hollywood box-office ratings. And Dr. Holly Phillips, a CBS medical contributor, said his extreme weight fluctuations may have contributed to the diagnosis.

As a baseball coach in "A League of Their Own" (1992), Hanks added 30 pounds. For the starring role in "Cast Away" in 2000, he reportedly shed 55 pounds to play a man fending for himself on a deserted island after a plane crash, CBS News reported.

Like Hanks, millions of Americans develop type 2 diabetes gradually. The American Diabetes Association reports that 25.8 million children and adults in the United States -- or about 8 percent of the population -- have diabetes, and the overwhelming majority has type 2 disease. However, fewer than 19 million actually have a diagnosis.

Another 79 million Americans have prediabetes, meaning their blood sugar levels are elevated.

People with type 2 diabetes have high blood sugar levels because they are unable to properly utilize insulin, a hormone needed to convert food into energy. Being overweight and sedentary are associated with the development of type 2 diabetes.

Many people with type 2 diabetes can control the condition through diet and exercise, but Hanks told Letterman he wasn't counting on weight loss as a solution.

"My doctor said 'If you can weigh as much as you weighed in high school you will essentially be completely healthy and will not have type 2 diabetes,'" said Hanks. "And I said, 'Well, I'm gonna have type 2 diabetes cause there is no way I can weigh as much as I did in high school.'"

Hanks said he weighed 96 pounds in high school.

Virginia Peragallo-Dittko is executive director of the Diabetes and Obesity Institute at Winthrop-University Hospital in Mineola, N.Y. She said: "We know Hanks has a 20-year history of prediabetes."

"He had a chance for 20 years to prevent making the transition to diabetes," Peragallo-Dittko added. "There is something you can do and the something is to lose 5 to 7 percent of your body weight and increasing your physical activity to 150 minutes a week."

Peragallo-Dittko said it's weight, not weight fluctuation, that results in diabetes.

There's also a genetic component to type 2 diabetes, she said. "You can choose your friends, but not your family. You're stuck with the genetic component. But your lifestyle is modifiable. A modest weight loss has a tremendous impact on preventing diabetes -- 5 to 7 percent is reasonable and has a big payoff," she added.

Diabetes medication, which can include pills and/or insulin injections, is prescribed for those who cannot control their blood sugar levels. It is not known what Hanks' doctor is recommending.

Uncontrolled diabetes can lead to serious complications such as heart and kidney disease, and amputation.

Dr. Jacob Warman, chief of endocrinology at Brooklyn Hospital Center in New York City, said: "Diabetes is a long-term disease that can be managed through diet, exercise, and medication. Because people often fail at diet and exercise requirements, we also put patients on medication right away. People with diabetes must stay away from simple sugars and eat complex carbohydrates. New medications, such as Metformin, have also shown to be effective in preventing complications and the need to go on insulin."

SOURCES: Jacob Warman, M.D., chief of endocrinology, Brooklyn Hospital Center, New York City; Virginia Peragallo-Dittko, R.N., BC-ADM, CDE, FAADE, executive director, Diabetes and Obesity Institute, Winthrop-University Hospital, Mineola, N.Y.; CBS News

Note: This article was published more than one year ago. The facts and conclusions presented may have since changed and may no longer be accurate.
Copyright © 2013 All rights reserved.

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