Jiroemon Kimura is not only the oldest person in the world; he is also believed to be the longest-lived human being in recorded history.

When Jiroemon Kimura was born 116 years ago, his native Japan was only about three decades removed from its period of feudal isolation and by then was embarking on a period of aggressive empire-building.

As a 7-year-old boy, Kimura may have heard that his country’s military had fought -- and beaten -- the Russians in a war. By his thirteenth birthday, Japan had annexed Korea as part of its growing Far East Empire.

By the time Kimura was a young adult, the Japanese Imperial army seized Manchuria in northern China; by 1941, when Kimura reached the age of 44, the Japanese bombed Pearl Harbor, launching the U.S. entry into World War II. He was not yet 50 when the Japanese surrendered to the Allies following the devastating atomic bombs that flattened Hiroshima and Nagasaki.

As the years passed, and Japan engineered an economic miracle turning the formerly isolated state into one of the world’s most powerful nations, Kimura kept on living and flourishing.

By his 114th birthday, Japan had endured the worst crisis of the post-war era -- the tsunami-earthquake of March 2011, which killed thousands of his countrymen and sparked a nuclear emergency scare.

The sweep of his epic life is utterly breathtaking.

Kimura, a former postman, is not only the oldest person in the world; he is also believed to be the longest-lived man in recorded history. He also holds the distinction of being the last known person to have lived in three different centuries.

The native of Kyotango City in western Japan retired from the post office at age 65 to take up farming, which he engaged in until he was a mere 90 years old.

Kimura has been feted by Kyotango Mayor Yasushi Nakayama, as well as by Japanese Prime Minister Shinzo Abe (by video).

Kimura lives at home with the widow of his grandson and eats three meals daily, according to BBC. He has 14 grandchildren, 25 great-grandchildren and 13 great-great-grandchildren.

Kimura’s motto is “to eat light and live long,” according to the Daily Mail. The centenarian refrains from smoking, consumes a “modest” amount of alcohol and eats only until his stomach is “80 percent full.”

But longevity is not at all unusual in the Land of the Rising Sun. Indeed, the world’s oldest woman, Misao Okawa, at a sprightly 115, is also Japanese.

Moreover, Kimura’s hometown boasts 95 people who are at least 100 years old; it's a city with a population of only 60,000. As such, city officials want to launch a research project on why its natives live so long.

"We would like to research the eating habits of not only Mr. Kimura but also about 50 other old people over 100 years old in the city," the official told Agence France Presse. "We are interested in what they eat and how much. We are especially keen to research on how much salt they consume. We are also interested in knowing what kinds of local food they like to eat and if this helps them live so long.”

Indeed, experts believe diet is key to Japanese longevity.

The average Japanese person consumes 86.2 grams of fat a day versus 155.4 grams for the average American, according to ABC News.

“I think Japanese food is very good compared with United States, because we don't eat much meat and we don't eat much sugar," professor Takako Sodei, who teaches gerontology at Ochanomizu University in Tokyo, said.

There is also a dark side to Japan’s large number of centenarians -- the overall population is rapidly aging, and the birth rate is falling to dangerous levels, posing troubling questions about the country’s future.

This past Tuesday, the government warned that Japan’s population dropped by a record 284,000 (or 0.22 percent) to 127.515 million as of last Oct. 1, while people age 65 or older passed the 30 million mark for the first time ever. People age 65 or older now account for almost one-fourth (24.1 percent) of the population, a new all-time record.

Meanwhile, the number of youths under the age of 14 fell to a record low of 13 percent of the population.

These trends have been oncoming for decades.

It is estimated that by 2055 40 percent of the Japanese population will be age 65 or above and most of them will not be working.

Put another way, Japan has too many nonworking elderly people and too few people of working age to support them. As this discrepancy widens in the coming years, the costs of taking care of the aged will become an ever-greater burden on the already overburdened Japanese of prime working age.

“We have never seen a country of the size and importance of Japan face these kinds of demographic issues before,” said Dr. Stephen Bronars, Ph.D., a Washington, D.C, senior economist with labor and employment consultancy Welch Consulting.

It is also believed that Japan's workforce will be cut by 18 percent by 2030.

“It's not just that the overall population of Japan will decline; the crucial issue is that the size of the labor force relative to the overall population will decline,” Bronars said.

Japan's average life expectancy is already the highest in the world -- as of 2008, it was 86.1 years for women and 79.3 years for men.

European nations like Germany, Italy and Spain (and even the U.S.) are experiencing similar aging demographic woes, but these countries allow relatively high numbers of immigrants to sustain and replenish their labor forces. By contrast, it is estimated that less than 2 percent of Japan's population is currently foreign-born.