Three years ago, Maureen Marinelli learned that she had a disease she didn't even know was a disease. She was diagnosed with impaired glucose tolerance, a symptomless condition in which blood sugar rises higher than normal -- enough to put you at risk of serious complications but not quite high enough to fit current definitions of type 2 diabetes.

Her lifestyle was one great big risk factor. A U.S. Postal Service employee and official for the letter carriers' union in Boston, Marinelli, 47, spent her days embroiled in hardball politics and delicate contract negotiations. At home, she was a single mom raising a teenage son.

"It's an understatement to say that my life was stressful," she says. "I ate on the run; my idea of a good lunch was a quarter-pound burger with cheese, fries and large soda. I weighed 189 and had high cholesterol, high blood pressure and reflux from all the stress." Too often, late-night stress relief was a pack of cupcakes or the newest barbecue potato chips. And she barely had time for her passion, tap dancing. ("I'm an old hoofer," she laughs.)

Marinelli's fortuitous early diagnosis may have helped her dodge the big "D": diabetes, a life-threatening disease that can lead to heart attack, stroke, kidney failure, blindness, amputation, even bone fractures and depression.

There are two types of diabetes. In both, the body can't remove sugar (glucose) from the bloodstream and deliver it to cells to use for energy. A small percentage of people have type 1, in which the pancreas doesn't produce insulin, the hormone that escorts glucose into cells. Most -- 90 to 95 percent -- have type 2: Their cells resist insulin's efforts to store sugar, and their body may also produce less and less insulin over time.