MORE THAN 2,000 YEARS ago, Huangdi Neijing, a classic Chinese medical text, identified obesity as a disease caused by eating too much “fatty meats and polished grains”. Until a generation ago, such a diet was an extravagance beyond imagination for all but the elite. But the Chinese waistline has since expanded, and at an alarming rate.

More than a quarter of the adult population, or roughly 350 million people, is overweight or obese (more than 60 million squeeze into the latter camp). That is at least twice as many as are undernourished. With rising incomes and more diverse diets, Chinese people are consuming much more fatty food and fizzy drinks. Meals now contain more than twice as much oil and meats than in the 1980s. This is producing a health calamity, both in heart disease (which now accounts for over a third of deaths) and in a less-noticed explosion of diabetes, which is closely linked to obesity. The prevalence of diabetes has grown more than tenfold during the past three decades. According to a recent national survey, 11.6 percent of Chinese adults are diabetic, a share almost as high as in America, whose obesity rate is much greater.

With a catastrophic famine still in living memory, it is little surprise that Chinese people have developed a taste for foods rich in fats and sugars. Fan Zhihong of the Chinese Nutrition Society says people who lived through the famine of the Great Leap Forward and the food shortages of the Cultural Revolution were keen to stop eating the coarse grains of the “dark old days” and have acquired a taste for refined grains and flour which are accomplices of diabetes.

Xiang Hongding, a diabetologist at Peking Union Medical College Hospital, says “some felt they’d better eat the good food now before it’s too late”. Nearly one in five Chinese aged 60 years and over is diabetic, twice the national rate.

The Chinese are not actually eating more as they get richer: the average daily intake has dropped a little over the past ten years, from 2,100 calories in 2002 to a little more than 2,000 today. This suggests a sedentary lifestyle may be hurting people’s health as much as changes in diet. Rapid urbanisation means more people are leaving the fields to work in less strenuous manufacturing jobs.

Meanwhile in the cities, walking and biking have been replaced by driving cars and sitting in public transport. Recent surveys show that less than 10 percent of urban dwellers exercise regularly.

Perhaps the most surprising consequence of urbanisation is that obesity is expanding even faster in rural China than in the cities.

Households on the fringes of cities are especially vulnerable: with farmland sold for development, many dispossessed farmers now spend their days sitting around and eating fatty meals. In 2012, public-health experts gave a warning that villages around Beijing might soon see their diabetes rates surpass rates in the capital.

That means the countryside is undernourished and overnourished at the same time. One is better than the other. But with spending on diabetes accounting for $25 billion in 2010 or 13 percent of the bills for health, over-nourishment is still an extravagance China can ill afford.

(Excerpted and adapted from )