For 20 years, the federal government has been issuing dietary guidelines in hopes Americans would adopt a healthier lifestyle. Over the same two decades, the percentage of Americans considered overweight (20 pounds over the ideal based on height and age) has actually increased, to 52%.

So as they convene a two-day federal nutrition and health summit-- the first major conference with top-level federal backing since a White House gathering in 1969--officials today plan to get more aggressive about the proliferation of diet doctors who promise quick weight loss with no pain. They are planning to fund research in government laboratories to see which popular diets actually help people lose weight, and which have no long-run impact--or even harm the patients.

The goal, according to government officials, is a much more sophisticated marketing campaign to reach ordinary Americans, most of whom don't know anything about the dietary guidelines the government has been issuing every five years since 1980. For example, less than a quarter of the population knows the "five a day" slogan, that five servings of fruits and vegetables daily helps reduce the risk of getting cancer.