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In Tokyo, the fast food of choice is a towering concoction of four hamburger patties, with all the trimmings, crammed into a single bun and children happily line up around the block for a calorie-laden doughnut.
But while the queues outside the Krispy Kreme doughnuts in the Shinjuku area of the capital, which opened recently, point to an extraordinary Japanese success story for the fast-food industry, they also symbolise a health disaster in the making for consumers.
Up to a fifth of Japanese children aged from 5 to 12 who are overweight suffer, or are at risk of developing, metabolic syndrome, with a range of symptoms including high cholesterol and large waistlines, according to a study released last week. Left untreated, it can lead to serious illnesses such as strokes and heart disease. Nationwide, the condition afflicts an estimated 23 million Japanese, the health ministry warns.
Although middle-aged "salarymen" are at greatest risk, children as young as 9 are now suffering from type-2 diabetes, a phenomenon unheard of in Japan only a few years ago.
Experts say the looming health crisis is being fomented by a surge in demand for highly calorific food sold by the top United States food chains.
When Krispy Kreme opened people waited more than an hour to sample its doughnuts. An estimated 10,000 people visited the restaurant in its first three days.
Burger King is about to launch its second assault on the Japanese market. Last week McDonald's in Japan reported monthly sales of just over 43 billion yen ($417.4 million), the highest in its 36 years in the country.
The US chain sold 1.7 million Mega Macs - four burger patties in a bun - in four days in Japan, as outlets struggled to keep up with demand.
Now diseases associated with obesity will strike Japan faster, and with greater ferocity, than anything seen in the West.
"When you have rapid transformations in lifestyles, that's when you see the worst health outcomes," says Tim Gill, Asia-Pacific co-ordinator for the International Obesity Task Force.
The rapid changes taking place in the Japanese diet, combined with a greater susceptibility to metabolic illness, will lead to dramatic rises in strokes, diabetes and hypertension, he warned. "The potential is there for a disaster," he says.
In the absence of Government intervention - limiting TV advertising aimed at children, or banning special promotions - the fast-food industry is enjoying unprecedented success in Japan.
"Krispy Kreme is the epitome of how to cram maximum calories into the smallest amount of food," Gill says.
"All you can do with doughnuts is to point out what crap they are."
More than 1300 people across the region have had weight reduction surgery since the beginning of last year, according to the Asia Pacific Bariatric Surgical Society.
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