Call it the ultimate dream diet -- you lose pounds while you sleep.

But the Federal Trade Commission said the diet product was only a dream -- it didn't work -- and it has filed suit against the marketer of Body Solutions Evening Formula, charging it with making false and unsubstantiated claims.

The diet formula marketed by Texas-based Mark Nutritionals Inc. was heavily advertised in both Spanish and English through endorsements from popular radio disc jockeys on more than 650 radio stations in 110 cities nationwide.

"Thanks to Body Solutions' lose-weight-while-you-sleep formula, I can have my bacon, sausage and grits and still lose weight," said one endorsement from an Atlanta DJ. "I've lost over 19 pounds so far and over an inch off my waistline."

The FTC said Mark Nutritionals sold more than $190 million in Body Solutions products. A 15-ounce bottle costs about $48, plus shipping and handling, and lasts about a month. One tablespoon is supposed to be consumed at bedtime, at least three hours after eating or drinking.

Yesterday's action was part of an FTC crackdown on misleading claims about weight-loss products. "We're actively looking for weight-loss products making the kinds of claims that can't be true," said J. Howard Beales III, director of the FTC's bureau of consumer protection. "To lose weight you have to eat less and exercise more."

In a recent workshop on weight-loss advertisements, FTC Chairman Timothy J. Muris put the media on notice, saying he believed it was the responsibility of newspapers, magazines and television stations to reject false and misleading diet and health ads. Beales reiterated those comments at a news conference yesterday. "We don't believe there is any constitutional protection for knowingly running false ads," he said.

Asked if putting the media in charge of overseeing weight-loss ads was like putting the fox in charge of the henhouse, Beales said, "Maybe it is, but right now the fox is asleep and profiting from running the kinds of ads" that concern the commission.

Nonetheless, the FTC did not bring any charges against the DJs, partly because of the large number involved, Beales said.

The FTC has reached a preliminary injunction with Mark Nutritionals precluding the company from using the term "weight loss" in the name of its product.

Larry Cochran, the firm's acting chief executive, praised the agreement for the "higher standards it sets in how the industry should promote and advertise its products." Cochran said the company plans to promote its product as part of a behavior-modification program instead of as a weight-loss regimen.