"I wake up at 6 am, then I will get some corn and go and feed the chickens or the pig," he says.
"I eat, but not as much ... generally beef, a good cut of pork, rice and beans -- four meals that we never went without in my house, thank God."
Guevara lives in the Nicoya peninsula of Costa Rica. Blessed with sandy beaches and tropical forest, it's something of a backpackers' paradise. It's also an area identified as a "Blue Zone" -- one of five hotspots around the globe where people live measurably longer lives.
Dan Buettner led the team that first discovered the Blue Zones more than a decade ago. Along with Nicoya, he identified Loma Linda, California; Ikaria, Greece; Sardinia, Italy, and Okinawa, Japan -- each of them selected because they have customs and lifestyles that help create an environment where people can live healthier, longer.
Buettner first visited the Nicoya peninsula in 2006, after demographers from the University of Costa Rica pinpointed what appeared to be a zone of longevity.
Relying on the country's accurate birth records they were able to hone in on the towns and villages where people were living the longest. An extensive door-to-door survey -- which included taking blood samples -- found lower cardiovascular disease and revealed something remarkable about telomere length -- the genetic biomarkers that are considered good indicators of aging.
Don't stress it
"Nicoyans have longer telomeres than the rest of the Costa Ricans -- especially nonagenarians and centenarians," explains Gilbert Brenes, of the Central American Center for Population. "The longer the telomere, the longer the life.
"Some scientists have argued that telomere length is a proxy for stress and what we've found is people in Nicoya are less stressed and have been less stressed throughout their lives than other Costa Ricans, and that helps in higher longevity," he adds.
Apart from avoiding stress, what's the secret of their longevity? No one know for sure, but there are some theories.
"Nicoyans specifically have a water that percolates through the limestone and it's very high in calcium and magnesium," says Buettner. "So quite literally, it might be a little bit in their water they tend to have fewer fatal broken hips -- their bones tend to be stronger.
"They eat mostly a plant-based diet, they live in villages where every time they go to work, every time they go to a friend's house, to church, there's a walk -- so they are nudged into some physical activity which keeps their metabolism at a higher rate."
He adds: "They tend to be people of faith -- we know people who belong to a faith-based organization, doesn't matter which one it is, Muslim Jewish Christian, they live four to 14 years longer than people who don't have that faith ... so it's an association but you'll see it very clear in Costa Rica."
Costa Rica spends only about one tenth of what the United States spends on healthcare, yet more than twice as many men there can expect to reach a healthy age 90. In fact, a University of Costa Rica study found that the probability of a 60-year-old Nicoyan male becoming a centenarian is seven times that of a Japanese male.
"This notion that you have to be rich to be healthy is completely wrong, and in Blue Zones we're almost wholly seeing longevity among people who would technically be well below the U.S. poverty line," says Buettner.
But life is about quality as well as and quantity, and make no mistake, the long lived of Nicoya are still enjoying the riches of life. At a party held recently, Guevara and 23 other centenarians showed what it means to be young at heart. Dr. Fernando Morales Martinez, director of the National Geriatric Hospital, made a four-hour trip from the capital for the historic gathering. It was a chance to listen and learn.
"I was surprised with all their answers because they were very coherent -- they explained everything and they were very good talkers and I was really amazed," he said. "What amazed me more was this lady of 108 years who asked me for dance."
That 108-year-old lady was Maria Francisca Isolina Castillo. Affectionately known as Panchita, she is the oldest resident in Nicoya. She lives in a humble home, and had four children, who have stayed close to her. Her oldest son, Pablo, is 92.
"Back in the day we ate meat from wild animals -- deer, paca, peccary -- animals from nature and not injected with anything," says Castillo. "Now almost everything you eat has been injected. That is why everyone is so lazy today!" she jokes.
Laughter is another important element in Blue Zone longevity, and a big part of what Costa Ricans call "pura vida" -- pure life.
As Brenes puts it: "Part of the secret in Costa Rica is to laugh and smile ... the pura vida motive shows that is part of it -- try to be happy!"