Obesity in China, particularly in children, has become an important health concern that will seriously affect the health of future generations but also place a heavy economic burden on the country. While China's GDP increased from $2.75 trillion in 2005 to $4.99 trillion in 2009, the number of obese people increased from 18 million to 100 million people, more than five times that amount, during the same period. "China has entered the era of obesity," Ji Chengye, a leading child-health researcher, told USA Today.

In addition, to make the situation even more serious, China, as well as Vietnam, India and many other developing countries, has to shoulder a "double burden" — the persistence of undernutrition, particularly among children in rural areas, and a rapid rise in obesity and related diseases such as cardiovascular disease, hypertension and stroke, Type II diabetes and certain forms of cancer.

"What we are seeing in developing countries undergoing rapid economic transition is undernutrition, overnutrition and infectious and chronic diseases coexisting over long periods of time," stated Gina Kennedy of the U.N. Food and Agriculture Organization.

Although the terms obese and overweight are sometimes used interchangeably, they have different meanings. Overweight is having a weight closer to normal than obese, and the difference between both terms is made using the body mass index (BMI), a way of determining the amount of body fat based on a person's weight and height.

Being overweight is not only a problem in developing countries but in industrialized countries as well. In the U.S., the number of overweight children has doubled and the number of overweight adolescents has tripled since 1980, according to the U.S. Surgeon General. In Chinese cities, according to official statistics, 8 percent of children 10 to 12 years old are considered obese and an additional 15 percent are overweight. A 2006 University of Southern California study found that the average body fat of Hong Kong children was 21 percent, an extremely high number.

The basic cause of obesity in children and adolescents is the energy imbalance between the calories they consume and the calories they expend through activity. But the increasing number of overweight and obese children and adolescents respond to many different causes.

There are several reasons to explain the increase in obesity in China. Traditionally, the Chinese diet included mainly cereals and vegetables, with few animal foods. As a result, fat and sugar intake remained low. However, as the country experienced explosive economic development, fatty and sugary food became much more widely available.

Due to the lack of knowledge in the general population of what constitutes proper nutrition, and about the harmful effects of fatty and sugary foods, their consumption has increased significantly, and so have the problems associated with it. Because of past famines in the country, different foods — particularly high fat foods — are now seen as highly desirable. At the same time, consumption of cereals, fruits and vegetables has decreased.

Eating in fast-food places, particularly American franchises like McDonald's, Pizza Hut and Starbucks, where food is particularly high in fats and sugar, is considered a status symbol. Although such places are expensive by Chinese standards, they offer an atmosphere of relaxation and luxury that attracts many Chinese, particularly young businesspeople.

Another important factor in the increase of obesity levels in the general population is inadequate physical activity levels. For instance, cars have become not only symbols of wealth, but have led to drastically lower levels of physical activity.

To confront this problem that has so many serious implications, it is necessary to increase programs in schools aimed at cultivating healthy eating practices and teaching healthy lifestyles. It is also important to increase nationwide social and health programs on public nutrition through the mass media and the creation of community-based nutritional education programs.

Several countries have been experimenting with the use of fiscal measures to limit the consumption of foods high in fat, sugar and salt. Higher taxes on unhealthy foods can help improve health by changing eating habits, while at the same time generating important revenue that can be used for prevention efforts.

The challenge for policymakers is how to develop effective programs and policies aimed at preventing and controlling this public health problem, while at the same time allowing the population to enjoy the benefits of the country's remarkable economic growth.

Dr. Cesar Chelala is an international public health consultant for several U.N. agencies and international organizations.