WASHINGTON -- Americans' sedentary lifestyle and poor eating habits are poised to overtake cigarette smoking as the nation's leading cause of preventable deaths, federal health officials reported yesterday.

Although tobacco is still the top cause of avoidable deaths, the combination of physical inactivity and unhealthy diets is gaining rapidly because of the resulting epidemic of obesity, officials said.

"Obesity is catching up to tobacco as the leading cause of death in America. If this trend continues, it will soon overtake tobacco," said Julie Gerberding, director of the federal Centers for Disease Control and Prevention, which conducted the study.

Based on current trends, obesity will become No. 1 by 2005, with the toll surpassing 500,000 deaths a year, rivaling the annual deaths from cancer, the researchers found.

"This is a tragedy," Gerberding said. "We are looking at this as a wake-up call."

In response, the Bush administration announced a new public education campaign, including a humorous advertising campaign that encourages Americans to take small steps to lose weight. In addition, the National Institutes of Health proposed an anti-obesity research agenda.

Tomorrow, a special task force will present the Food and Drug Administration with formal recommendations on what that influential agency can do to help reverse the cresting public health crisis.

"Americans need to understand that overweight and obesity are literally killing us," said Health and Human Services Secretary Tommy Thompson in a statement.

Critics, however, immediately denounced the moves as inadequate, saying the administration should take tougher steps to encourage healthier eating and force the food industry to improve their products and stop advertising junk food to children.

"If the government said, 'You really ought to cut back on soft drinks and juice drinks,' those lobbyists would go berserk. They don't want to take on the food industry," said Marion Nestle, a professor of nutrition and public health at New York University. "The focus is all on physical activity. It's perfectly safe. It's totally uncontroversial. But it's not enough to keep weight under control."

The new estimates of the rising toll of obesity come in the first update of a landmark paper that ranked the nation's preventable causes of death in 1990.

Cigarette smoking, which increases the risk for a host of illnesses including lung cancer, emphysema and heart disease, topped that list. But anti-smoking campaigns have led to a steady decline in the number of Americans who use tobacco, slowing the rise in the resulting toll of illness and death.

In the new analysis, which is being published in today's Journal of the American Medical Association, Gerberding and her colleagues conducted a comprehensive analysis of the medical literature and analyzed preventable deaths for the year 2000.

Tobacco still topped the list, accounting for 435,000 deaths, or 18.1 percent of the total. But poor diet and physical inactivity were close behind and rapidly gaining, causing 400,000 deaths or 16.6 percent. That represented a dramatic change from just 10 years earlier, when tobacco killed 400,000 Americans (19 percent) and poor diet and physical inactivity killed 300,000 (14 percent).

In 1990, the third leading cause of preventable death, alcohol, was responsible for 100,000 deaths. By 2000, that number had dropped to 85,000.

But despite intense public concern, the number of Americans who are overweight or obese has continued to rise, reaching epidemic proportions. In 1990, about 15 percent of adult Americans were obese. By 1990, that number had climbed to 30 percent, with 65 percent being overweight.

The new findings come a day after another study concluded that if current trends continue, one out every five dollars spent on health care in the United States will go toward obesity-related treatment by the year 2020.

The trend was not surprising, given the skyrocketing obesity rates, said Richard Atkinson, president of the American Obesity Association. But the problem calls for a more intensive, innovative response, Atkinson said.