Actress, activist, author and fitness guru Jane Fonda spoke and signed copies of her new book at Kepler's bookstore in Menlo Park on Aug. 18.

"Prime Time: Making the Most of Your Life" aims to provide a comprehensive blueprint for healthy, fulfilled living well into what Fonda calls the Third Act of life.

Via email, she answered questions about longevity, its effects on humanity, and activism for seniors.

Q: There are other books about living well in old age. What inspired you to write "Prime Time," and how does it add to the conversation?

A: There are many books out there on aging, some very good, none that cover the gamut as my new book does. There are books called things like "How to Live to be 100," catchy sorts of titles that promise all sorts of things. There are many books about how to extend your lifespan (not supported by most scientists), how to do financial and legal planning for the Third Act, books about wisdom and soul.

But none that I know of include all those subjects along with issues of intimacy and how to maintain a safe and pleasurable sex life as you age things people have told me they have never been able to find out about elsewhere. As my editor says, "This is a very generous book." I have done four years of intense research and I am very proud of what this book can bring people.

Q: Recent reports show that San Mateo County residents live longer than just about anyone else in the country. Are we buying more of your videos? What are we doing right?

A: That's terrific! I know that Loma Linda (in Southern California) is one of what are called "Blue Zones," which are places where there is an unusually high number of centenarians. The reason this is true in Loma Linda is because many of that town's population are members of a religion (Seventh-Day Adventist) that encourages healthy eating and lots of physical exercise as a normal part of their days.

Q: How should those still in Act II be "rehearsing" for Act III? What about those in Act I?

A: I have heard from a number of people in their forties who have already read my book and tell me they learned a great deal about how to begin preparing for their Third Act. I offer many questions that readers can ask themselves about people and events in their first and second acts -- questions that will help them understand themselves better -- what they can change and what they can't about their character and personality.

Act II is a perfect time to start thinking about the future. For example, begin a life review. This was so important to my own sense of well-being now as I age. Begin to think about savings and budgeting. Start becoming more physically active if you haven't already.

Q: You talk about a "longevity revolution" changing everything, including what it means to be human. Expand on that bold statement.

A: When you add a new room onto a house, it isn't just that new room that is different -- how you use the entire house is altered. This is a good way to think about the 34 years that have been added to the average American lifespan over the last century. It represents an entire second adult lifetime.

This changes (or potentially changes) our notions of marriage, of relationships in general, of how we pace ourselves through life. We are able to experience our own species' effects on the planet in ways we couldn't when we only lived to an average of 45 years.

Q: In addition to your work with fitness, you're known for passionate social and political activism. Is that sort of thing compatible with old age or is that strictly a younger person's game?

A: Activism is not only compatible with old age, it is quite usual for people, women in particular, to become more radical when they're older. We have less to lose. We're beyond the pleasing stages.

I feel our task is to mentor, encourage, teach the younger generations and to use our increasing numbers, ongoing zest (Post-Menopausal Zest, or PMZ, as Margaret Meade called it) and wisdom to make the world a more peaceful, equitable place.