If you want to live to a healthy old age, eat the way healthy old people do.

That was Dan Buettner’s idea when he set out to research his new book, “The Blue Zones Kitchen: 100 Recipes to Live to 100,” which has landed on the New York Times bestseller list.

Buettner has been studying and writing about longevity for 15 years, ever since he and a couple of colleagues used demographic data to pinpoint the places in the world where people live the longest. As they zeroed in, they used blue ink to outline the top areas for ideal aging, giving birth to the name “Blue Zones.” Buettner then visited the zones to “reverse-engineer longevity,” he said, coming up with a blueprint for lifelong good health.

That original project, undertaken for National Geographic, resulted in a cover story for the magazine and the first of three bestsellers, “The Blue Zones: Lessons for Living Longer From the People Who’ve Lived the Longest.” It also spawned Buettner’s current work creating programs with cities to “nudge citizens to eat less, move more and socialize more.”

Over the years, Buettner, of Minneapolis, has watched Western diets and fast food move into the once-healthy Blue Zones, resulting in lower life expectancies and soaring rates of obesity. He has mourned the loss of the old ways of life — which revolved around family, friends and community, and included natural movement like walking, a sense of purpose and daily rituals.

He also became concerned about what would happen to traditional Blue Zones recipes, some of which had been passed down for generations, as the older people who prepared them began to die.

“These are recipes that fueled people into their 90s and 100s,” he said.

Buettner wasn’t planning on becoming a cookbook author, but he decided to return to all five Blue Zones to capture and preserve the old recipes. With National Geographic’s backing, he went to Sardinia, Italy; Okinawa, Japan; Nicoya, Costa Rica; Ikaria, Greece, and Loma Linda, Calif., where a cluster of Seventh-Day Adventists who eat according to guidelines laid out in Genesis live.

He parachuted into kitchens to, as he said, “watch old women — it’s almost always women — cook,” taking notes on ingredients and methods, tasting and sampling as he went. The explorer/journalist/quasi-anthropologist brought along his dad, Roger, 84, as a taste-tester.

“He is the quintessential Middle American,” Buettner said. “He grew up in Staples [Minn.] on a farm, milking cows and eating pork chops. His thumbs-up gave us a high degree of comfort that Americans would like a recipe. For example, he gave seaweed and fermented tofu thumbs-down.”

Commit to quality

Buettner returned home with about 250 recipes, then had a team convert them from “a handful of this and pinch of that” into standard measures. Then he whittled the number of recipes to 100.

The best way to use the book, he said, is to keep trying recipes to see which ones you absolutely love, until you have about six to put into regular rotation in your diet.

“The most important ingredient in any recipe is taste,” Buettner said. “It’s delusional to think that if you don’t like eating a plant-based diet that you’ll eat it for any amount of time. You have to find what’s so delicious to you that no one has to remind you to eat it.”

Consistency counts, because it’s eating nutrient-rich dishes over years that builds long-term health. Quality food, Buettner said, is 60% of the path to living longer.

“The four pillars of every longevity diet in the world are nuts, whole grains, greens and beans,” Buettner said.

The Blue Zones diets are 90 to 100% plant-based, with meat, dairy and sweets making rare appearances. Cooks in these areas tend to use the same 20 or so ingredients in different combinations. Flavor comes from spices and herbs.

In Ikaria, the main herbs used for cooking and teas are oregano, rosemary, sage and catnip. Buettner’s team sent the island’s herbs to the University of Athens School of Pharmacology for testing, and found these herbs have anti-inflammatory or diuretic properties.

The flavor profiles from each zone are different, so Buettner hopes there’s enough variety in the cookbook to please almost every palate.

Cooking healthy habits

Home cooking is critical to living longer with good health, too.

“There’s good research to back this,” Buettner said. “Every time you go out to eat you consume 200 to 300 more calories than you would if you cooked at home. Moreover, it’s an activity you pass down to your children, who are picking up lifelong learning habits before they’re about 13. Passing down cooking for healthy eating gives them a skill for life.”

Buettner also recommends slowing down to eat these home-cooked meals, having observed the daily rituals of the Blue Zones that promote a critical sense of belonging and connection as well as physical health.

“Pausing, sitting with family and friends — some people say a prayer, some talk about their days — it’s giving you the 20 minutes it takes for the feeling of fullness to travel from the belly to the brain. In Okinawa, the culture is to stop eating when you’re 80 percent full.”

It’s a bonus that in most Blue Zones, socializing also happens over coffee, tea and, yes, wine. Water is the main beverage consumed in all Blue Zones. But other drinks have their benefits.

The homemade wine favored by Sardinians made from grenache grapes, for example, contains exceptionally high levels of polyphenols and anthocyanins linked to heart health. Those who drink it a couple of times a day have a lower mortality rate than those who don’t drink at all. (Although Buettner cautions that that’s not a reason to start drinking if you don’t already.)

“In America,” Buettner says, “we’re marketed the idea that we should add superfoods, or shakes or the next trend to our diet. But the vast majority of us will die of overnutrition — of heart disease, many types of cancer, diabetes and even dementia.

“So instead of thinking about what to add, think about what to subtract. In the Blue Zones, you take calories out of the day by doing things like removing the TV from the kitchen — cook and eat while talking to your family, instead — and by eating breakfast like a king, lunch like a prince and dinner like a pauper.”

For years, Buettner said, he focused on data and statistics to make his arguments about how to live longer. Finally, with this book, he says he’s found the key to more people understanding his message.

“It starts with food,” he said. “Delicious food.”