U.S. health officials say obesity and inactivity could soon overtake tobacco as the leading cause of preventable deaths in the United States.

The U.S. government's disease tracking agency, the Centers for Disease Control, or CDC, says smoking is still the leading cause of death in the United States. But agency director Julie Gerberding says tobacco-related deaths might not hold the lead for long.

"Tobacco and obesity are the Number One and Number Two causes of death," she said. "That is similar to what we saw in 1990. But the big change is that obesity has actually almost caught up as the leading cause of death in this country."

Dr. Gerberding and colleagues outlined the growing health threat from obesity in a study published in the Journal of the American Medical Association. They report that smoking caused 100,000 more U.S. deaths than obesity in 1990. But, by 2000, the gap had narrowed to just 35,000.

"If these trends continue, we are going to see obesity overtake tobacco as the leading cause of death in this country," said Dr. Gerberding. "We've got to do something about both of these problems. As a nation, we are used to appreciating the epidemics of infectious disease threats that plague us, but we have got to regard these problems as epidemics, also. Tobacco-use and obesity are truly problems of epidemic proportion."

Together, they account for one-third of all U.S. deaths, according to Centers for Disease Control data.

However, tobacco is a waning habit in the United States, while overeating and lack of exercise are becoming more widespread. The American Medical Association says two-thirds of U.S. adults are either overweight or obese. A recent study in another of its journals, the Archives of Internal Medicine, showed that obesity costs the nation $90 billion a year and 300,000 premature deaths.

Dr. Gerberding and other top U.S. health officials have announced a nationwide program to alert Americans to the dangers of the problem. It involves an advertising campaign and steps to motivate local communities to begin fitness programs. To combat smoking, the agency is expanding its telephone help lines for people seeking smoking cessation programs and related services.

"We've got to all take the steps necessary to combat tobacco and obesity and these other preventable causes of death," she said. "The clinicians and our health care delivery system need to step up to the plate [take action] and address tobacco use and obesity as major health threats. Schools need to play a larger role in getting kids to exercise and have better nutritional choices in the school room."

In recognition of the obesity epidemic, the giant U.S. fast-food restaurant chain, McDonald's, recently announced that it is phasing out "supersized," or extra-large, portions, in its U.S. establishments.

The problem, however, is not restricted to the United States. Obesity is now a looming specter wherever countries are undergoing a shift to urbanization, modern technology and food processing, and more leisure time.

University of Rhode Island anthropologists have found that the greatest increases in average body weight since the early 1950's have been among people in developing countries. The World Health Organization will present an anti-obesity strategy at its annual meeting of national health ministers in May.

A draft version unveiled in January calls for tighter regulations on food advertisements, taxes on junk food and soft drinks, and other regulatory and education programs. If adopted, the WHO program would not be binding on countries. News reports say the United States government has lobbied for a softer strategy, but critics of the Bush administration accuse it of blatant pandering to U.S. companies that produce foods high in fat and sugar.