About 20 years ago, working for National Geographic, and with a grant from the National Institute on Aging, I started identifying and studying the longest-lived people, those who are in what we called the world’s Blue Zones. These are people who have eluded heart disease, diabetes, dementia, and several types of cancer.

My goal, in a sense, was to reverse-engineer longevity. Since only about 20% of the average person’s life span is dictated by genes, I reasoned that if I could find the common denominators among people who’ve achieved the health outcomes we want, I might distill some pretty good lessons for the rest of us to follow. I discovered nine powerful lessons—the power nine—that underpin all five Blue Zones. Here they are:

1. Move naturally.

The world’s longest-lived people don’t pump iron, run marathons, or join gyms. Instead, they live in environments that constantly nudge them into moving without thinking about it. They grow gardens and don’t have mechanical conveniences for house and yard work.

2. Find purpose.

The Okinawans call it ikigai and the Nicoyans call it plan de vida; for both it translates to “why I wake up in the morning.” Knowing your sense of purpose is worth up to seven years of extra life expectancy.

3. Downshift.

Even people in the Blue Zones experience stress. Stress leads to chronic inflammation, associated with every major age-related disease. What the world’s longest-lived people have that we don’t are routines to shed that stress. Okinawans take a few moments each day to remember their ancestors, Adventists pray, Ikarians take a nap, and Sardinians do happy hour.

4. Follow the 80% rule. . .