MANILA, March 12 — A wave of obesity is sweeping through Asia as its population shifts into vast new cities where the food is faster and fattier and the lifestyle more sedentary.

As it did in the West a generation ago, obesity is bringing with it a range of ailments led by cardiovascular disease. Once uncommon in Asia, diseases of the heart and cardiovascular system are now the continent's leading killers.

Most visibly and most dangerously for the future, obesity is spreading among children, bringing a severe form of diabetes and putting them at risk for years to come.

Known in Chinese as "xiao pangzi," or "little fatties," these roly-poly children seem to be everywhere, the pampered victims of cultures that prize them as emblems of affluence and well-being.

"We spoil him," said Warisa Waid, a Thai teacher in Bangkok, of her 11-year-old son, Saharat, whose father is an ethnic Thai-Chinese. "Whatever he wants, we give it to him. We don't care if it is good or bad, we just feed him whatever he wants.

"Plus his lifestyle," she added. "He spends most of his time in front of the TV, playing video games and watching cartoons."

When Saharat was younger, his mother said, he was small for his age. "His father's family believes that being skinny is bad, so they kept telling me, `Why don't you feed your kid more,' and, `What's wrong with him.' "

Now he is too fat, she said, but his grandparents keep feeding him.

"He loves deep-fried stuff, and very minimal vegetables," she said. "Almost, I could say, he doesn't eat vegetables at all. They give him whatever he wants — KFC and McDonald's and pizza and all that."

In other words, a typical Asian city boy.

In cities, it is processed foods and fast foods rich with sugar and saturated fats that are the most available and often the cheapest. At the same time, there is much less demand or opportunity for physical exercise.

Over and over, studies show much more obesity in cities than in the countryside. In China, 5 percent of the population as a whole is classified as obese; in its fast-developing cities, the number can be as high as 20 percent.

Many of these are children, particularly the "little emperors" in China, where government-mandated one-child families often cause parents to be overindulgent.

The World Health Organization now reports that 6 out of 10 deaths in the region are due to diseases that may be linked to obesity — heart attacks, stroke, diabetes, hypertension, gallbladder disease and some forms of cancer.

While obesity can be a crucial factor in all these ailments, it is the direct cause of two-thirds of diabetes cases and one-fifth of all heart disease. In most Asian countries, these diseases now take more lives than do malaria, tuberculosis, pneumonia, malnutrition, accidents and other more familiar causes of death.

The spread of obesity may prove more deadly here than in the West. For the most part, these are not developed nations. Their health care systems cannot cope with such complex diseases and their expensive, long-term treatments.

"Asia is facing a nutrition crisis, and what is at stake is the health of half the world's population," said Neville Rigby, spokesman for a London-based medical association called the International Obesity Task Force.

This comes at a time when the rates of cardiovascular disease have been dropping in many developed nations because of public education, treatment and screening programs.

Unlike communicable diseases with their immediate symptoms, obesity has crept up almost unnoticed and Asian governments are unprepared to address it, said Dr. Gauden Galea, a Philippines-based expert with the World Health Organization. "We are talking about numbers so huge that people can't see them, even," he said.

Overall statistics for the region have not been collated, he said. "It's more like a jigsaw that emerges from many individual studies that all fit together."

Globally, more than one billion adults are overweight and at least 300 million of these are classified as obese. Asians are making up an increasing proportion of these, he said.

A particular concern is the rapid spread among Asian children of what was once known as adult-onset diabetes. The ailment, which rarely affected children in the past, is so closely linked to obesity that it has been nicknamed "diabesity." In China, experts say, it has been rising by 9 percent a year.

"We are faced with kids aged 10 to 12 who may require treatment for the next 50 years with tablets or insulin shots, and start getting heart attacks at age 25 to 30," said Paul Zimmet, director of the International Diabetes Institute in Melbourne, Australia, at a recent conference.

The World Health Organization, in a report last week, said 30 million people in East and South Asia have adult-onset diabetes — one-fourth of the world's cases in an area that is home to about half the world's population. It projected that the number would rise to 130 million by the end of this decade, more than half the projected worldwide total of 216 million.

The danger of cardiovascular disease is heightened in Asia by widespread smoking, the third major risk factor, along with poor diet and lack of exercise. In addition, Asians are more susceptible to these ailments because they tend to store fat around the abdomen, which puts a particular strain on the heart and cardiovascular system.

Experts set benchmarks using a "body-mass index" that involves height and weight in a continuum from simply overweight to obese. As the body-mass index rises, so do health risks. However, Asians encounter health risks with lower body mass indexes and smaller waists than Caucasians do.

The public health challenge is compounded by the fact that most Asian nations are still dealing with the opposite problem — food shortages in much of the population.

"More than any other region in the world, Asia faces two quite different diet-related health problems: undernutrition and overnutrition," said the Asia Food Information Center, a private group.

In Vietnam, for example, the government Center for Nutrition found in the year 2000 that 12.5 percent of children in Ho Chi Minh City, the former Saigon, were obese. At about the same time, the government was announcing a plan to try to reduce the nationwide malnutrition rate among children.

Experts say governments will be faced with difficult choices in allocating health-care funds between those who eat too little and those who suffer from eating too much.

Dr. Galea cautioned against blaming the overeaters for their condition, which he said was as much the product of their environment as an infectious disease would be. "When people move to cities they are automatically at greater risk," he said — the poor as well as the more comfortably off.

It is not only the fast-food chains that have changed the Asian diet. Milk, ice cream, cookies, soft drinks and potato chips — these once-alien foods are as common in many parts of Asia now as in the West. Meat and eggs are making inroads on rice and vegetables.

In the last two decades, Thais have doubled their annual intake of sugar to 63.9 pounds per person from 27.9 pounds, according to a study in 2001 by the Public Health Ministry.

"Sugar is everywhere in our lives, in food, desserts, soft drinks, snacks and even infant milk formula," said Dr. Supreeda Adulyanond of the Thai Health Promotion Foundation.

The World Health Organization reports that obesity among Thai children aged from 5 to 12 rose to nearly 16 percent from 12 percent in just two years.

In Japan, researchers found that from 1970 to 1999 the prevalence of obesity among 9-year-old boys had risen from 2.9 percent to 9.7 percent. Among girls, the number rose from 3.4 percent to 8.

In Malaysia, reports show that obesity among teenagers increased to 6 percent in 1997 from 1 percent in 1990.

In the Philippines, Dr. Augusto D. Litonjua, who heads the Philippine Association for the Study of Overweight, a private group, said that in an informal survey of doctors, 25 percent of patients were overweight.

He blamed what he called "malling," which he defined as spending the day in shopping malls and eating at fast-food restaurants.

Even as they eat, however, many of these people long to be slim. As in the West, the bloating of Asia has been accompanied by a slimming of the ideal of beauty. As American fast-food chains spread through Asia they are being followed by a proliferation of gyms, slimming programs, diet pills and liposuction.

From Taiwan to Thailand, models and movie stars look like their counterparts in the West, long-boned waifs, never satisfied that they are thin enough.

"I think I am fat," said Methinee Kingpayome, one of Thailand's most famous models. "Although people think I am thin, I can always find fat on my body."

She added the obligatory disclaimer for people who make their living from their good looks, "True beauty is not judged by physical appearance but by the kindness of the heart."