At first glance, the news that Japan is the world's healthiest nation is something of a surprise. This, after all, is a country with notoriously high levels of pollution and one of the worst suicide rates on the planet.
Walk into a coffee shop and the smog confirms that Japan is a smoker's paradise - more than half the male population light up regularly. Or take a midnight walk around the neon-lit entertainment districts of Shinjuku or Namba and it's clear from the crumpled figures on the pavement that this is also a land of heroic drinking - and a growing alcohol problem. Yet for all this, the 126 million Japanese can expect to live longer and more active lives than anyone else, according to a new report from the World Health Organisation. The average healthy life expectancy in Japan is now 74.5 years, comfortably ahead of France, in second place with 73.2 years, and leagues ahead of Britain, in 14th spot with 71.7 years.
The most commonly cited and convincing explanation is Japan's traditional low-fat and varied diet. Raw fish, green tea, seaweed and pickled plums (so sour that they make your eyes water) are all believed to contribute to some of the lowest rates of cancer and heart disease in the world.
Take the Abe family, a fairly typical household living on the outskirts of Tokyo. Steelworker Hideo Abe is a smoker and a drinker but he expects to live past 70. The reason, he says, is that his grandparents and great grandparents all lived well into their 90s on a diet that was very similar to his own.
The Abes start the day with a bowl of miso and tofu soup, white rice and a few strips of nori (laver seaweed). As a breakfast, it might not sound as tasty as a British fry-up, but it wins hands down in terms of calories and good nutrition.
For lunch, Mr Abe orders a "bento", a boxed meal that contains at least 10 different - all neatly compartmentalised - types of food ranging from pickles and salad to fish and the staple white rice. Mothers send their children off to school with similar bentos, which ensure a far more balanced diet than the usual British fare of sandwiches or meat and two-veg. Mr Abe also makes sure he has a piece of fruit.
For the evening meal, Mrs Abe prepares numerous small dishes. Fish is usually the main one - more than half of the Japanese intake of protein comes from the sea. On the occasions when the Abes do have red meat, they prefer it as "shabu shabu": wafer thin slices of meat that are boiled for just a few seconds.
The Abes wash these meals down with green tea. Although it's made from the same leaves as the black tea popular in the west, it is not fermented, which means it retains more polyphenols, antioxidants that are believed to fight cancer. It is also drunk without milk or sugar, which ensures less fat and fewer calories.
The Abes enjoy alcohol, but like many Japanese, they have recently cut down on beer and sake, and started drinking more red wine. Underlining the health-consciousness of the country, imports of Burgundy have more than tripled since researchers found that red wine may reduce the risk of heart disease.
Such a diet helps to explain why Japanese waistlines are less likely to bulge. Obesity is three times lower than in America and, as a result, there is a less risk of a heart attack or diabetes.
But food alone cannot explain why the country is so healthy. The state has also played a key role, not only as a nanny, but as a nurse, policeman and personal trainer. To keep the nation in trim, the state-run NHK channel broadcasts music and instructions for calisthenic exercises at the crack of dawn each day. More importantly - and unlike the US, which was 24th on the WHO list - Japan is a truly egalitarian society. Once described as the only successful example of socialism, Japan has an average wage of £22,000 and high standards of health care that are within reach of almost everyone.
Change, though, is on the way, with western food and habits gradually catching on. Fat intakes are on the up and fitness levels are declining. Even Mr Abe acknowledges that he may not live as long as his ancestors. "Our generation is different. We've probably had it too good to be really healthy."