The Food and Drug Administration launched a broad anti-obesity campaign yesterday that will include revising the familiar nutrition label on food packages to make it easier for people to count their calories.

The agency also will crack down on food companies that make it hard to discern how many servings are in a container; define when products can be labeled as containing "low" or "reduced" carbohydrates; and encourage development of a new generation of weight-loss treatments, officials said.

"Far too many Americans are literally eating themselves to death," said Health and Human Services Secretary Tommy G. Thompson. "The epidemic of obesity threatens the health of millions of Americans."

The plan capped a week when the nation's mounting obesity crisis became the focus of intense new attention, underscoring rising alarm and tension over the issue among public-health experts, federal officials, consumer advocates, the food industry and Congress.

With two-thirds of Americans now overweight or obese, federal health officials warned Tuesday that the nation's weight problem is overtaking tobacco use as the leading cause of preventable death. The same day, the Department of Health and Human Services unveiled a public education campaign and a scientific research agenda on obesity at the National Institutes of Health. In contrast, the next day the House approved a controversial measure that would protect food companies against lawsuits by people who blame them for their weight problems.

Yesterday's announcement came as a result of a set of recommendations from a task force convened by the FDA to propose ways the powerful agency could help fight the problem.

"Obesity is one of America's greatest health challenges today," said FDA Deputy Commissioner Lester M. Crawford. "More Americans are overweight or obese than ever before, and this has significant implications for our health."

A person is overweight if the body mass index, or BMI, is between 25 and 29.9, and obese if the BMI is more than 30. To calculate BMI, divide weight in pounds by the square of a person's height in inches and multiply the result by 704.5.

Food companies and restaurants generally praised the moves and pledged to work with the government to counter the rising number of Americans who are overweight or obese. Consumer advocates and some members of Congress, however, criticized the steps for relying too heavily on voluntary action.

"Overall, the administration is . . . rearranging the deck chairs on the Titanic," said Michael F. Jacobson of the Center for Science in the Public Interest, a consumer group. "Relying on junk-food marketers' self-policing is naive and one of the things that helped Americans waddle into the obesity epidemic in the first place."

Officials defended the strategy, saying a number of companies had already begun taking steps voluntarily, such as McDonald's eliminating "supersizing," Ruby Tuesday providing nutrition information on its menus and Krispy Kreme considering a lower-calorie doughnut.

"I believe voluntary compliance in this case is much better," Thompson said. "If this doesn't work, then we're going to have to come back and take a harder look at it and find more kinds of actions that are going to be more oppressive."

The agency plans to revise the nutrition panel required on all packaged foods to make the number of calories more prominent. Among the proposals is increasing the size of the type used to display the calorie count and including what percentage it represents of the daily recommended caloric intake.

"For many consumers, counting calories is . . . very stressful and can be very confusing. You cannot lose weight if you eat more calories than you burn. Calories in must equal calories out," Thompson said.

The agency also sent letters to food manufacturers warning that it planned to be more aggressive about policing how labels count the number of servings in a package. Some labels are inaccurate or mislead people into overeating by dividing packages into unrealistically small serving sizes, officials said.

The task force concluded that companies should "label as a single serving those food packages where the entire content of the package can reasonably be consumed on a single eating occasion," Crawford said. "This is something food companies can do now under the existing regulation." If companies fail to comply, they could face fines and other penalties, he said.

The agency also planned to consider allowing companies to make health claims for some foods that meet the FDA's definition of "reduced" or "low" in calories, such as: "Diets low in calories may reduce the risk of obesity, which is associated with type 2 diabetes, heart disease and cancers."

Because of the surge in interest in carbohydrates, the FDA will start defining what foods can be labeled "low," "reduced" or "free" of carbs, officials said. "We think to a large extent that these moves will demystify the current confusion about carbohydrates," Crawford said.

The guidelines the FDA uses to evaluate weight-loss drugs date to when amphetamines were the most common diet drugs. As a result, the agency will convene an advisory committee to review and update the guidelines in light of current scientific understanding, officials said.

"We need to change it for two reasons. One is to get into conformity with the science as it exists but also to send a signal that FDA is interested in receiving these kinds of applications," Crawford said.

At the same time, the agency plans to more aggressively encourage restaurants to provide more nutrition information on their menus so Americans can monitor their diets while eating out. That move drew criticism from those advocating mandatory nutritional information in restaurants, given how often most Americans eat outside the home these days.

"We must move beyond recommendations to immediate action," said Sen. Tom Harkin (D-Iowa). "More aggressive steps to curb obesity and give consumers the tools to make healthy decisions are necessary to address this growing crisis."

"For many consumers, counting calories is . . . very stressful and can be very confusing," Health and Human Services Secretary Tommy G. Thompson said.