How Well You Age Can Depend on You

Kyna Iman, 45, of St. Louis, works out, eats right and comes from a family whose members have a history of living past 80.

She eats a healthy diet and exercises three days a week at the Fitness Factory in downtown St. Louis.

"I have an aunt in her 80s with diabetes," Iman said. "And she's healthier than I am and gets around more than me. That's how I want to be."

Scientists say what's most important about Iman's outlook is that she made a choice to live healthy years. Your longevity is largely in your hands.

What Is Aging?
Aging is how fast your cells wear out; that starts when they divide.

"Each time they divide, the two new cells are (lower quality) than the first cells," said Dr. David R. Thomas, professor of medicine at St. Louis University School of Medicine. But no one knows why. Science generally is stumped by "why do we age and what kills us," Thomas said.

Dr. Michael Roizen, co-author of the "YOU..." series of personal health books, says that cells also wear out when they're mistreated -- smoking, drinking too much alcohol, eating too much fatty food, being sedentary.