How To Live To Be 100

They trigger our awe and our nostalgia as representatives of a flinty, hardscrabble culture that hardly exists today. They lived out a parable of man at one with nature. They used their bodies as they were designed and programmed over the millennia: for walking, for working, for being fed from the earth's natural bounty. It makes one wonder whether the next generation of oldsters will last quite as long. They will need not just the luck of the genetic draw but also the strength to renounce the lure of fast-food days and couch-potato nights that add yards of butt lard and shorten life-spans by years.

Will Americans in the supersize age resolve to go medieval on their own bodies? It would help, if they want to live to 100. As Poon says of his research pools, "I don't have any fat centenarians." And if research really does extend life by a vigorous couple of decades, the new millions of centenarians will need a support system that spreads beyond family and friends to include a hugely expensive Social Security and Medicare apparatus. The coming gerontocracy won't come cheap.(See how to prevent illness at any age.)

But that's for the future. Any child of today who hopes to live into the 22nd century without the aid of medical miracles should look to the past, and consider the lessons today's centenarians took from the 19th century. There's a poetry of common sense in their scheme for immortality. Eat sensibly. Keep walking. Keep knitting. If you can't keep friends, make new ones. Plan so much invigorating work that there's just no time to die. And no regret when you do.

— Reported by Alice Park/New York; Melissa August/Washington; Anne Berryman/Athens, Georgia; Hanna Kite/Okinawa; Chris Lambie/Halifax; Jeff Israely/Sardinia; and Francis X. Rocca/Rome

See the world's most influential people in the 2011 TIME 100.

See TIME's 140 Best Twitter Feeds.