Americans, often guilty of overeating, should cut harmful fats, get more exercise and watch their weight under a new set of U.S. government dietary guidelines being written by nutrition experts.

A preliminary version of the rules for healthful eating, unveiled on Thursday, flatly tells Americans to cut consumption of saturated fat, trans fat and cholesterol.

The draft guidelines also warn Americans not to eat more food than they need, to “be physically active every day,” and to eat more fruits, vegetables and whole grains, to reduce the chance of chronic illnesses such as cancer and heart disease.

Two-thirds of U.S. adults are overweight and childhood obesity is ballooning. Poor diet and physical inactivity, blamed for 400,000 deaths a year, may soon overtake smoking as the No. 1 cause of preventable death.

Panelists were unable to finish their work and set another meeting for Aug. 10 and 11 to wrap up suggestions for the new edition of the Dietary Guidelines for Americans, slated for release in January. First published in 1980, the guidelines are updated every five years to reflect new research on nutrition.

Often reduced to a handful of short reminders, such as “choose and prepare foods with less salt,” or a pamphlet, the Dietary Guidelines also are a 44-page document expanding on the pithy advice.

If it follows the committee’s proposals, the new edition would explicitly tell Americans to balance food intake with physical activity while eating a variety of foods. The current advice is “aim for a healthy weight.”

Overeating “is a big problem right now,” said panelist Penny Kris-Etherton, a nutrition professor at Pennsylvania State University.

A long-standing admonition to “moderate your intake of sugars” was dropped from the tentative guidelines. Panel members disagreed whether sugary drinks lead to obesity.

“I don’t like targeting a single item,” said Theresa Nicklas of the Baylor College of Medicine. Joanne Lupton of Texas A&M University said research found no clear result.

Carlos Camargo of the Harvard Medical School said three studies showed a link. Many people do not offset calories from drinks by eating less food, he said.

Panel members settled on language saying people who consume food and beverages high in added sugar consume more calories overall and that “sugar-sweetened beverages are not as well-regulated as calories in solid form” by the body.

Experts acknowledged that the 2005 guidelines were unlikely to include any major changes.

“We’re really talking about a fine-tuning of messages,” said Regina Hildwine, senior director of food standards for the National Food Processors Association. “I think there are going to be some opportunities here for food companies,” she said, such as those selling foods that use more whole grains.

Margo Wootan of the activist group Center for Science in the Public Interest said America’s bulging waistline was the result of eating too-large portions of food, She called for easy-to-follow advice on trimming calories from the diet.

While advising Americans to eat less saturated fat, trans fat and cholesterol, linked to clogged arteries, the advisory committee gave a green light to omega-3 fatty acids, found in fish. Omega-3 acids reduce the risk of cardiovascular disease, researchers say.

But the panel noted there should be a general warning about mercury in fish. The government said in March that shark, swordfish, king mackerel and tilefish contain too much mercury to be eaten by pregnant women, nursing mothers, children and women who may become pregnant. Adults can eat up to 12 ounces (340 grams) a week of seafood lower in mercury.