(FORTUNE Magazine) – The me generation has a lot to answer for: go-go boots, the Monkees, smiley faces, Donald Trump. Still, we boomers have gotten many things right. We fixed beer. We put more women in the executive suite. Now we're working on our best move ever: upgrading middle age.

To see the fix being installed, look around the local fitness center. You're likely to find dudes in bifocals pumping iron, moms of grown-up kids doing serious laps, AARP members slamming racquetballs, and scarily fit fortysomethings like Texas Instruments CIO Brian Bonner (on the cover). This isn't narcissism; it's attitude. To our parents, 39 conjures up Jack Benny cracking wise about being over the hill. To us, it's a perfectly reasonable age at which to take up snowboarding or to start having kids. And why not, considering that 40-year-olds today are roughly seven years younger, in terms of average remaining years of life, than their grandparents were at that age?

Once we do hit 40, we'll very likely live to see 65. Whatever disease will ultimately kill us--cancer, heart disease, Alzheimer's--probably won't have gotten us by then. That's particularly true for college-educated professionals, since they tend to do more things right: Compared with the general population, they smoke less, weigh less, and eat less fat and more fruits and vegetables. (Heart disease, lung cancer, and diabetes in middle age are increasingly blue-collar ailments.) Definitive studies reported in the past two years suggest that the small fraction of middle-aged Americans who really take care of themselves--from exercising daily to munching leafy greens aplenty--have about 80% lower risk of heart disease than their typical peers. Americans who take better care of their hearts have cut midlife mortality from some major forms of cancer. Nonsmokers very rarely get lung tumors, and those who exercise and stay lean significantly lower their risk of colon cancer.

For all these reasons and more, midlife is no longer about winding down. It has evolved into a phase of maintaining health, preventing and detecting stuff that can kill us, and managing whatever problems we do have. Baby-boomers can be intense about such issues. We reflexively rebel--or should, anyway--when a doctor says, "You're just getting old, so of course your hearing/potency/backhand is going." That doctor likely doesn't have the time or inclination to assess all the cutting-edge prevention and treatment options for us (thanks, managed care!). We have to learn to do it ourselves.

The following pages offer a fast head start. You'll find up-to-the-minute advice on a dozen health issues, from colon cancer screenings to wrinkles, that really matter to Gen B-ers--and to all who aspire to live long and well. Oh, yeah: There are also tantalizing tidbits from Michael Jordan's trainer about how Jordan, nearly 39, has managed once again to show what the incredible baby-boomer body is capable of. Yep, fellow boomers, the bald Wizard wearing No. 23 is one of ours.

--DAVID STIPP

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