I was talking about career paths and power with two top women at a lunch Friday: Sharon Allen, an Idaho farmer's daughter who grew up to be chairman of Deloitte USA, and Lisa Weber, the daughter of a New Jersey taxi driver who is now president of MetLife's (MET) so-called individual business -- a hulking enterprise with $19 billion in revenues and some $1.5 billion in operating profits. I knew both Allen and Weber before -- they come to Fortune's annual Most Powerful Women Summit, which I chair. And Weber's been on our annual Most Powerful Women in Business list since 2004.

But until you get talking about the personal stuff, you don't realize how these top-tier women made it big by breaking out of their comfort zones. Early in her career, when Allen was managing Deloitte's Boise office, she was an able manager. But her crucible came, she says, when she moved away from Boise to Portland and then to Los Angeles to run bigger offices. "One of my managers told me, 'You're so much better outside of Boise. When you're in Boise, you're a manager; outside of Boise, you're a leader, because you have to rely on other people.'"

Weber tells a similar story. She spent most of her career in HR -- typically not the route to the corner office. When Rob Henrikson, MetLife's CEO, asked her to take the big operating role, she practically said no. "I didn't know if I would be successful," Weber says, "since I didn't have a sales background. But later I realized that what I was being asked to do was not about sales, but leadership." Out of her comfort zone, she learned to rely on people to help her -- which really is the essence of leadership, isn't it?

Weber, 45, drives herself hard. A Manhattan mother of two kids, she rises each morning at 3:45 a.m. -- no, not to work. To run eight to 10 miles. That's the shot of energy she needs to get through her day. Weber has completed eight marathons already. Now she's training for another.

Weber and Allen were on a panel I led for the Forte Foundation, a consortium of corporations and business schools that aims to get more women to the top -- largely by encouraging young women to go to business school. Fascinating coincidence that neither Weber nor Allen have MBAs. Both talked about the value of business degrees. But you have to wonder, would MBAs have helped them move any faster?