Five hours of largely laudatory testimony from doctors and nutrition advocates left little doubt that the Bloomberg administration’s plan to ban trans fats in restaurants is headed for approval, but the city’s top health official yesterday signaled that the administration might alter its proposal amid concerns from the food industry.

The city’s Board of Health heard from dozens of medical experts, dieticians, and industry officials in the only scheduled public forum on separate proposals to phase out the use of the artery-clogging artificial fats and to require some restaurants to prominently display the amount of calories in each of their menu items.

In their scope and ambition, the proposals mirror the city’s ban on smoking in bars and restaurants, imposed in 2003, and they have drawn similar cries from some detractors that the government is overreaching. But at yesterday’s hearing, held in a crowded chamber on 125 Worth St. in Lower Manhattan, supporters far outnumbered opponents, and to a large extent criticism was limited to the logistics of implementing the regulations, not to their intent.

The Bloomberg administration also received a boost shortly before the hearing when Kentucky Fried Chicken held a news conference down the street to announce it would remove trans fat from nearly its entire menu, including its signature crispy chicken wings, legs, and strips. The president of KFC, Gregg Dedrick, said the company had spent two years testing cooking oils that were free of trans fats before it found a suitable soybean oil.

“There is no compromise,” Mr. Dedrick said. As part of the official announcement, KFC employees dressed in red aprons personally delivered buckets of fried chicken to more than 40 news outlets across the city.

Like many restaurants and national chains, KFC now uses a partially hydrogenated frying oil that contains trans fat, an acid that in recent years have been shown to increase the risk of coronary heart disease. Doctors blame trans fat for at least thousands of deaths a year.

Mr. Dedrick said the company has already started converting to its new oil in major markets, including Manhattan, and it expected to complete the switch nationwide by April.

The move by KFC comes four months after the nonprofit Center for Science in the Public Interest sued the company for using trans fat. The announcement drew praise from the city health commissioner, Dr. Thomas Frieden, who said he was “delighted” that KFC has decided to eliminate trans fat from its cooking oil.

Still, KFC is not going as far as the city is demanding restaurants go. Under its current plan, trans fat would be removed from 80% of its products, but it would remain in items such as chicken pot pie, biscuits, macaroni and cheese, gravy, and some desserts. Mr. Dedrick said KFC was working on finding alternatives to trans fat for these items, but the company gave no timeline for when a switch would occur.

Under the administration’s proposal, the city’s more than 24,000 restaurants would have to remove trans fat from oils, margarines, and shortening within six months. They would have 18 months to make all other items trans fat-free.

Mr. Dedrick also did not say whether KFC supported the city’s proposal to require restaurants to display caloric information on menus and menu boards. Many fast food chains, including KFC, already post nutritional information on brochures, packaging, or on their Web sites, but city officials say this is inadequate because consumers often read the information after their purchases, not before.

Large chains have criticized the proposal as unfeasible. At yesterday’s hearing, a vice president for Wendy’s, Mark Inzetta, sought to demonstrate the point by unfurling a several-foot long poster with more than 250 menu combinations and their calorie amounts written in small lettering.

Mr. Inzetta said Wendy’s, which no longer uses trans fat, already displayed much more detailed nutritional information on a separate poster hung on the walls of its restaurants.

He also derided the city’s proposed labeling mandate as “discriminatory,” as it applies only to eateries that already make nutritional information publicly available, and not to all restaurants. The city has said about 10% of restaurants in the five boroughs fall into that category, mostly large chains.

In criticizing the trans fat ban, restaurant industry officials said a year-long city campaign to urge restaurants to eliminate trans fat on their own was woefully inadequate, citing surveys that showed many restaurant owners had never heard from the city and some did not even know what trans fats were.

The food industry also said owners needed much more time to switch to healthier cooking oils and shortening, claiming there was not currently enough supply in the market to accommodate the thousands of city restaurants.

“This cannot be accomplished overnight, nor even in 18 months,” the executive vice president of the New York State Restaurant Association, Charles Hunt, said.

Dr. Frieden dismissed that argument, telling reporters outside the hearing that the city accounts for just 2.8% of the nation’s population. “We’re confident that there’s ample supply of trans fat free healthy alternatives,” he said.

When asked if the city might amend its proposal before the Board of Health votes in December, the commissioner said, “Absolutely.”

“We listen carefully to what people have to say,” he said. “We consider, honestly and sincerely, whether we need to make a change to make this even better to protect the health of New Yorkers and even more feasible to have to implement it.”

The proposed ban had plenty of support from nutrition advocates, and dozens gathered at a rally at nearby Thomas Paine Park. “People are innocently making themselves sick without knowing it,” the founder and director of the Institute for Integrative Nutrition, Joshua Rosenthal, told the board.

The board heard a different view from a former Libertarian candidate for mayor, Audrey Silk, who aggressively opposed the administration’s smoking ban in 2003. “Eliminating choice and coercing behavior is not the American way,” Ms. Silk said. She added: “Our bodies aren’t yet the property of the state.

Saying the trans fat ban was a matter of public health, Mayor Bloomberg offered an impassioned defense of the proposal as he campaigned with Senator Lieberman yesterday in Connecticut.”Government does have a responsibility to go and to try to improve the longevity and the quality of life of its citizens,” he said, citing the prohibition on lead in paint and asbestos in buildings as examples. “There are times when it becomes so important that the government just has to say ‘No more.'”