Japan suffers from many trends that trouble the remainder of the developed world, including a falling birth rate, a rapidly aging population, rising health care costs for the elderly and a stagnating economy.

But happily, Japan isn’t burdened so much by one of the gravest health care crises sweeping across virtually all other wealthy nations: obesity.

According to data from the Organisation for Economic Co-operation and Development, or OECD, as of 2009, only about 3.5 percent of the Japanese population was classified as obese, versus rates as high as 30 percent or greater in the U.S. and elsewhere.

Part of the reason for Japan’s svelte figures is explained by their adherence to a traditional diet of brown rice, fish, broth-based soups, fruit and vegetables and a minimal consumption of red meat.

Naomi Moriyama, co-author of a book titled “Japanese Women Don't Get Old or Fat: Secrets of My Mother's Tokyo Kitchen” told WebMD that the Japanese not only eat healthy foods, but in smaller portions than usually consumed in the West.

"Thanks to the relatively healthier Japanese diet and lifestyle, Japanese women and men live longer and healthier than everyone else on Earth," Moriyama said.

Indeed, the Japanese live about five years longer than their counterparts in the U.S. and with far lower rates of disability and illness.

Moriyama estimated that the average Japanese person consumes 25 percent fewer calories daily than the average American.

Also, culturally and socially, obesity is anathema in Japan.

In 2008, the Global Post reported, the Tokyo government established a maximum waistline size for people above the age of 40: 33.5 inches for men and 35.4 inches for women.

Under Japan’s health care coverage rules, employees who fail to meet waistline guidelines are forced to undergo counseling.

Indeed, if Japanese firms don’t cut the number of overweight employees by 25 percent by the year 2015, they may be required to pay more money into health care programs for the elderly.

Along with the aging population, health care costs are projected to double by 2020.

Despite the prevalence of generally slim figures in Japan, obesity rates, along with diabetes, have been climbing for the past three decades, partially due to the adoption of some Western diet customs, like fast food.

But a blogger on CalorieLab wrote that obesity will likely never become a serious problem in Japan, citing three major factors: peer pressure, the necessity of exercise and small meals.

“Japanese society is largely based on how one fits comfortably and unabrasively into society, way more so than most Western societies,” the blogger wrote.

“There is a huge amount of peer pressure to conform, and the pressure on women in particular to stay slim is tremendous.”

Regarding the inevitable exercise, she commented: “Usually people who live in Japan, especially the urban and suburban areas, just have to move a lot more. Cars aren’t practical at all except for longer trips, so almost everyone commutes by public transportation. ... People just naturally get more exercise than in a typical American city.”

Finally, ”the average portion sizes are still quite a bit smaller than in the U.S.”

In March 2012, an article in Japan Times signaled a warning about the dangers of eating Western-style fast food.

Gozoh Tsujimoto, director of the Drug Discovery Research Center at Kyoto University, told the paper: “Lifestyle factors [in Japan] have become Westernized. Especially, food has become Westernized -- and mainly high calorie and high fat.”

Indeed, there are about 3,600 McDonald’s restaurants now in Japan, making it the fast-food giant’s second-largest market, just after the U.S., which has almost 13,000.

Tsujimoto advised that people “reduce the fat content of meals, eat meals with increased levels of fiber and plants, eat fish” and “take moderate exercise and avoid alcohol.”

The devastating tsunami/earthquake that battered much of northern Japan in March 2011 had at least one bizarre and unexpected consequence – it contributed to higher rates of obesity among the children who live in Fukushima, the vortex of the nuclear emergency that the natural disaster precipitated.

Japan’s Asahi Shimbun newspaper reported that children in the Fukushima Prefecture had the highest obesity rates in Japan in seven age groups, citing statistics from the education ministry, likely due to a lack of exercise as parents are fearful of letting their kids play outside due to the perception of lingering radiation.

"Children cannot play outdoors [even apart from gym classes], so they now engage in less physical exercise," a local education board official said. "That may be one cause."