WASHINGTON (AP) _ Weight loss company executives Monday told a congressional panel examining ''rampantly misleading advertising'' that dieters with a lot to lose should expect a long ordeal despite ads promoting quick results.

''The claim to lose weight quickly can be a very appealing claim,'' Weight Watchers Inc. President Peter Berger said at a House Small Business subcommittee hearing. ''But there are recognized speed limits of one to two pounds a week.''

But Berger defended a Weight Watcher's ad that says dieters can lose three to five pounds the first week.

''Week one is an unusual week. Most people lose a lot of weight, mostly a liquid loss,'' Berger said. ''We believe in slow and steady, but too slow can be discouraging.''

The session was one of a series subcommittee chairman Rep. Ron Wyden, D- Ore., has held on diet programs, which each year generate about $33 billion in revenues but are governed by few federal regulations.

''It's high time some standards were put in place to do something about the rampantly misleading advertising in the field,'' Wyden said.

Representatives of Jenny Craig International, the Diet Center, Physicians Weight Loss Centers, Nutri-System, Optifast, Medifast and other weight loss groups or institutes also attended the hearing.

The witnesses said weight loss was best achieved by eating nutritional food in moderation and doing simple exercising.

Representatives of liquid diet programs said they can show obese people, those with more than 50 pounds to lose, faster results. But they said such clients should be monitored by physicians.

''Our average patient is more than 60 percent above the ideal weight, carrying around an extra 80 to 100 pounds of body weight,'' said William Rush senior vice president of Sandoz Nutrition Corp., which operates hospital- affliated Optifast diet programs.

Wyden said he was skeptical about the safety of the various programs.

''I am most concerned about this extraordinary push to help people lose weight quickly,'' Wyden said. ''Rapid weight loss has been linked to numerous health problems.''

He pulled out a Diet Center advertisement that said: ''You can lose 10 pounds in two weeks, be two sizes trimmer in three weeks.''

''That relates to the earlier weight loss people experience in the first weeks,'' said Jim Liljenquist, Diet Center senior vice president for corporate communications. ''But this ad has been discontinued.''

Ellen Destray, vice president of Jenny Craig International, said she expected reforms in diet company advertising as a result of Wyden's hearings.

Wyden said there were no standards for training people in the diet business or to warn people if they are in a weight category in which dieting should be supervised by doctors.

Some of the weight loss professionals agreed that federal regulations should be developed; others said the industry could police itself.