For instance, a beverage company should label a 20-ounce bottle of soda as containing 275 calories instead of 2.5 servings of 110 calories each — as is often the case today — since most people drink the whole bottle at one time.

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

The move is part of the FDA's new strategy for fighting obesity. It is aimed at teaching Americans to think closely about calories when they choose what to eat, FDA Deputy Commissioner Lester Crawford said.

"America must get back to the basics," Crawford said. "There's no substitute for the basic message — that calories in must equal calories out."

Crawford said the FDA has mailed letters to food-manufacturing companies encouraging tem to "take advantage of the flexibility in current regulations on serving sizes" to be more realistic in defining such servings.

The FDA working group responsible for the recommendations also proposed that the calorie content of foods be brought into sharper relief on food labels — by increasing type size and stating the product's percentage of daily caloric needs.

Other proposals include encouraging the restaurant industry to list caloric values of their meals, enhancing public education about healthy eating and encouraging research into healthy new foods.

The agency's strategic plan against obesity came days after a scientific study reported that obesity is about to outstrip tobacco exposure as the leading preventable cause of death. Deaths from illnesses related to poor diet and inactivity increased 33 percent between 1990 and 2000, according to the study.

Michael Jacobson, executive director of the consumer advocacy group Center for Science in the Public Interest, said in a statement that "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."

James Hill, director of the center for human nutrition at the University of Colorado, said there was nothing wrong with highlighting calories, but the public needs a better way to understand what those numbers mean.

"Five hundred calories — what does that tell you?" Hill said. "It would be better if you had something saying this amount of calories would require so many minutes of walking, for example, to burn off."

Thompson's comments were reported by The Washington Post.