Trying to devise a one-size-fits-all description for ultraprocessed foods is flummoxing federal regulators.

For months, the health secretary, Robert F. Kennedy Jr., has promised to create a definition of ultraprocessed, a crucial part of the Make America Healthy Again agenda. In mid-April, he testified before Congress that the Food and Drug Administration had forwarded a definition to other agencies, including the Department of Agriculture.

But behind the scenes, officials said, the process of defining ultraprocessed foods is still very much up in the air. Agencies are struggling to agree, and it is unclear when a definition will be released.

“It’s not final until it’s final,” said Calley Means, a senior adviser to Mr. Kennedy, adding that the definition would ultimately be the result of hundreds of conversations with scientists, agency staff and other stakeholders.

For the food industry, which is already seeing demand for many of its products soften as some consumers cut back on spending while others use weight-loss drugs, the debate about what an ultraprocessed food is or isn’t has potentially far-reaching consequences.

Under one classification widely used among the scientific community, essentially any foods or drinks made with ingredients you wouldn’t find in a home kitchen are defined as ultraprocessed. If regulators adopt that sort of definition, nearly three-quarters of foods sold in the United States could be deemed ultraprocessed.

The food industry is arguing against a strict definition that would label chicken nuggets, strawberry yogurt and whole-grain tortillas as ultraprocessed.

Based on that definition, deli turkey could be categorized the same as a snack cake, the National Turkey Federation wrote in a comment letter to regulators last fall. It said that certain food additives and processing steps were critical to keep turkey fresh and that those “benefits are especially important for lower-income households, where access to nutrient-dense, high-quality protein can otherwise be limited.”

One fear that emerged in interviews with food companies, lobbyists and regulators, most of whom declined to be quoted, is that foods tagged as ultraprocessed could be restricted or eliminated entirely from the nation’s school meal programs. They are multibillion-dollar revenue streams for the companies that make sandwich breads, cereals, salsas and other foods. Others are worried that regulators could create new rules for warning labels on the packaging of foods in grocery stores.

But Mr. Kennedy, who has frequently referred to ultraprocessed foods as “poison” and has suggested restricting them from the diets of Americans, particularly children, is facing intensifying pressure from the MAHA movement, which is credited with helping elect President Trump to his second term. A Politico poll published in April showed that removing ultraprocessed foods from the American diet was a core principle for people identifying as MAHA followers.

“If we can have a federal definition that is strong and science-based, it opens the door for meaningful policy,” said Vani Hari, a health advocate who is known as the “Food Babe” online and is a prominent voice in the MAHA movement. And, she added, “anything positive that is coming out of the administration on food reform is popular with voters.”

Many scientists support a strong definition, and noted that evidence linking ultraprocessed foods to a host of chronic diseases, including obesity, Type 2 diabetes, heart disease and some types of cancer, has grown in the last decade.

Defining ultraprocessed foods is “one of the most important policy actions around food that the U.S. government has done for probably 25 years or more,” said Dr. Dariush Mozaffarian, a cardiologist and the director of the Food Is Medicine Institute at Tufts University. “Industry is going to fight tooth and nail because this is a fundamental threat to their entire model,” he added.

Dr. Mark Hyman, a physician and friend of Mr. Kennedy’s, called ultraprocessed foods the “single biggest threat to public health ever.” He characterized the food industry’s lobbying on the definition as “their usual shenanigans.” It is “obfuscating, confusing, undermining credibility of scientists,” he said.

While the food industry is trying to make its case to federal regulators, it is also facing a dizzying array of new regulations by states. Emboldened by the MAHA movement, many states are not waiting for the federal government. Instead, they are writing their own rules for food. Last year, Texas and Louisiana passed laws that required warning labels on foods that contained any of 44 additives, while California banned certain ultraprocessed foods from school lunch programs. Other states are weighing similar moves.

Dr. Mozaffarian at Tufts and some other health experts argue that the federal definition should adhere closely to a food classification system called Nova, which is used in the vast majority of the research linking ultraprocessed foods to poor health.

The Nova definition deems a wide swath of products ultraprocessed, including candy, soda and hot dogs. It also includes some foods traditionally considered to be healthy, like many whole wheat breads, peanut butters and yogurts.

The definition is focused primarily on ingredients. Peanut butter, if it contains nothing more than peanuts or salt, would not be considered ultraprocessed. But most peanut butters sold in grocery stores contain hydrogenated vegetable oils, kicking them into the ultraprocessed category, according to Nova. Likewise, plain yogurt would not be considered ultraprocessed. But when ingredients like emulsifiers and flavorings are added, the food becomes ultraprocessed.

In his testimony before Congress in mid-April, Mr. Kennedy said that once a definition was in place, his agency would move forward with a plan that would mandate placing color-coded labels on the front of food and beverage packages.

“If it’s a red light, don’t eat it,” he said during his testimony. Green, he said, would signal to consumers the food is healthy.

Mr. Kennedy also suggested that following a federal definition of ultraprocessed foods, states could restrict them from their food stamp programs — jeopardizing billions more in revenue to food companies.

In conversations with regulators and members of Congress, the food industry broadly asserts that an overly strict definition of ultraprocessed foods like the one from the Nova system could target nutritious foods, that more research is needed, and that increased regulation could result in higher prices for consumers.

Using a broad brush to categorize foods “fails to capture the important reality that all processed foods are not equal,” the cereal manufacturer WK Kellogg wrote in a comment letter last year when the F.D.A. asked about how ultraprocessed foods should be defined. The National Chicken Council wrote in another comment letter that “gummy bears and chicken nuggets in this comparison are technically ‘ultraprocessed’ by common definitions. Yet, it is clear which one has potential to contribute meaningful nutrients to a higher quality diet.”

Some of those arguments are gaining traction inside the Department of Agriculture, which oversees the nation’s school meal programs. Officials there say it is unclear if the definition will be tied to policy and, if it is, expressed concern that food manufacturers could quit the programs, leaving school officials with fewer choices for children’s lunches.

Lindsey Smith Taillie, a professor of nutrition at the University of North Carolina’s Gillings School of Global Public Health, who met with F.D.A. officials in mid-April, said there was a middle ground. She argues that regulators can still create a strong federal definition similar to Nova’s while constructing useful policies — such as for warning labels or school meals — by exempting products that are “healthy,” according to F.D.A. standards.

The F.D.A. defines a healthy food as one containing a certain amount of actual food — like fruits, vegetables or milk, as opposed to processed ingredients like cornstarch — and not too much saturated fat, sodium or added sugars.

Dr. Taillie said most ultraprocessed foods don’t meet the “healthy” definition. But a policy like this could motivate food companies to reformulate products to fit that criterion, she added.

The president of Bard College, who has run the unorthodox liberal-arts school for more than a half century, announced his retirement on Friday, after the release of documents that showed he had a closer relationship with Jeffrey Epstein than previously known.

The president, Leon Botstein, was known for his fund-raising prowess and outsize personality, but came under scrutiny after the release of a trove of documents collected by the Justice Department related to Mr. Epstein. The files showed Dr. Botstein had exchanged messages and visits with Mr. Epstein for years, including after Mr. Epstein’s conviction on solicitation of a minor for prostitution.

In one 2013 note, Dr. Botstein signed off with “Miss you.” He spoke of his cherished “new friendship” with the financier, and wished him well after the publication of news article that detailed his abuse.

The college commissioned an independent review, conducted by the law firm WilmerHale, and the findings were released on Friday.

The review found that Dr. Botstein had done nothing illegal but that his relationship with Mr. Epstein raised concerns about his leadership. The review said that Dr. Botstein had ignored the concerns of a senior faculty member who advised him that Bard should avoid Mr. Epstein.

“President Botstein forcefully argues that Bard’s need for funds was paramount,” the review concluded. “His view was, ‘I would take money from Satan if it permitted me to do God’s work.’”

The review noted that Mr. Botstein had visited Mr. Epstein’s island, invited Mr. Epstein to stay at Bard and to visit a high school affiliated with Bard, and had taken payments from Mr. Epstein. Mr. Botstein said he had in turn funneled those payments to Bard under his own name.

Dr. Botstein has long maintained that his relationship with Mr. Epstein was entirely about coaxing him to give money to the school, which is about 100 miles north of New York City.

Dr. Botstein became president of Bard in 1975, when he was only 28 years old and the college was in dire financial shape. He earned a reputation as a talented fund-raiser, and is credited by his supporters with keeping Bard afloat at a time when many colleges are facing difficulties and some have closed.

In 2021, the billionaire George Soros pledged to donate $500 million to Bard’s endowment, which now tops $1 billion.

The new documents did not show any criminal wrongdoing on Dr. Botstein’s part, but Dr. Botstein is the latest powerful person to leave a top position after their communications with Mr. Epstein were revealed.

Dr. Botstein said in a statement Friday that he believed it was in the “best interest of Bard” to wait until the review was complete before he announced his retirement.

In the statement, he said that he would continue working as a professor and participating in music programs connected to Bard. Since 1992, Dr. Botstein has been the principal conductor and music director of the American Symphony Orchestra. In his statement, he said he would also live at Finberg House, an on-campus residence hall.

Billing itself as “a private college in the public interest,” Bard has long prided itself on bucking the conventions of higher education. The college doubled down on its bohemian sensibility under Dr. Botstein’s leadership.

The out-of-the-box thinking extended to college admissions. Bard applicants, for example, can skip the traditional process and instead submit three lengthy essays.

And Dr. Botstein has lampooned the U.S. News and World Report rankings, which many college leaders swear by.

He has also been a strong advocate for early college, creating some of the first programs that allow teenagers, often from underrepresented backgrounds, to earn college credit tuition-free while still in high school.

But when it came to another convention of modern higher education — the need to raise private money — Bard embraced the practice. Dr. Botstein said he hated raising money from the wealthy, describing it as a humiliating experience.

Still, in his statement Friday, he said that the college under his watch had secured nearly $3 billion in philanthropy. He said he would stay as president until the end of this academic year, June 30.

It was fund-raising that brought Dr. Botstein into contact with Mr. Epstein. Dr. Botstein has said that the relationship with Mr. Epstein began with a small, unsolicited donation by the sex offender in 2011. “A guy sent us money and we followed up,” Dr. Botstein told The New York Times in 2023. “It’s a simple story.”

But after the latest release of documents, Dr. Botstein’s explanations for various interactions with Mr. Epstein often left community members with even more questions.

For instance, after the documents showed that Dr. Botstein’s office had planned a trip to Mr. Epstein’s island in 2012, Dr. Botstein said he had become sick during the trip and wasn’t sure whether he actually stayed on the island. When The Times reported an email from Dr. Botstein from the day after that 2012 trip, in which the president thanked Mr. Epstein and wrote “the place is great,” Dr. Botstein, through a spokesman, said he was referring to “the overall environment of St. Thomas.”

The WilmerHale report said Dr. Botstein was not “fully accurate” in describing his relationship with Mr. Epstein in public statements.

The documents also showed that the two had worked together to buy an expensive watch. Dr. Botstein, a watch collector, explained that he was helping Mr. Epstein, who had expressed interest in a watch, buy one.

Dr. Botstein kept the timepiece for about a year before Mr. Epstein demanded Dr. Botstein return it or begin making payments to cover the $56,000 cost.

In one email, Mr. Epstein even excoriated Dr. Botstein, describing his purchase of the watch as “careless.”

The initial response to the news was subdued on the Bard campus, and it appeared many, including board members, were willing to stand by a leader viewed by some as central to the college’s success over the decades. But the pressure mounted after a slow drip of news coverage.

This spring, the board of trustees, headed by the billionaire James Cox Chambers, announced it had hired WilmerHale to investigate Mr. Epstein’s relationship with the president and Bard.

The faculty senate eventually weighed in on the matter, urging trustees to “plan for a transition in leadership.” The faculty statement also called for envisioning a Bard after the man who had led it for more than half a century.

The board on Friday thanked Dr. Botstein for “his countless accomplishments and the lasting impact of his leadership.” It said it will soon announce an interim leader and the details of a national search for the next president.

Students at Cornell University had gathered on Thursday for an evening of debate over the war in Gaza and the long-running conflict between Israelis and Palestinians. The debate rapidly escalated after the event, during a walk with the university president to the parking lot.

As students posed critical questions and surrounded his car, the university’s president, Michael Kotlikoff, said that the students banged on his vehicle when he tried to drive away, an accusation they deny and that video provided by the students does not show.

The confrontation on the Ithaca, N.Y., campus was a reminder of the lingering tensions over the war between Israel and Hamas and how universities responded to student protests, even as on-campus demonstrations have largely subsided.

The evening had been billed as a civil dialogue between supporters of Israel and backers of the Palestinian cause.

As night fell and the debate ended, Dr. Kotlikoff, who had spoken at the event, walked to his vehicle, a black Cadillac SUV. The video shows it slowly reversing, as a handful of students stand behind and around the vehicle recording the incident. The car stops in front of one student, brushing him. It then accelerates and bumps into the student, causing him to stumble.

A second student screamed that the car had run over his foot, though video does not show a clear angle of that happening.

“You’re running a student over? Am I allowed to stand here?” Hudson Athas, 21, the student who was bumped, said before the car lurched.

Dr. Kotlikoff continued backing up and left the parking lot. Emergency medical technicians arrived and checked the foot of the second student, Aiden Vallecillo, a 22-year-old senior, who was not seriously injured.

The students’ campus organization, Students for a Democratic Cornell, described Dr. Kotlikoff’s behavior as “reckless.” In a statement released by the university, Dr. Kotlikoff described himself as the victim of the incident, saying he had experienced “harassment and intimidation” that was aimed at “silencing speech.”

Dr. Kotlikoff said that he had been followed to his car by a group of students who were “loudly shouting questions” at him. In his telling, the students had been “banging on the windows” of his car and blocked his exit. The video does not show the students hitting his car.

The students who confronted Dr. Kotlikoff on Thursday said they were objecting to the suspension of student demonstrators and measures that they said stifle free speech on campus. Those include restrictions on protest, as part of the school’s “expressive activity policy,” which was adopted in March 2025.

It was not their intention to block his car, they said.

Dr. Kotlikoff said that he waited to back out until he saw space behind his car and was able to “slowly maneuver my car from the parking space.”

Like many universities in the United States, Cornell erupted with student protests in the spring of 2024 over the Israel-Hamas war. And since October 2023, when that war began, the university has issued more than 80 disciplinary actions, including suspensions, against students that it says have infringed on “the rights of others.”

The suspended students include the leader of the campus encampments movement, Momodou Taal, a Ph.D. student in Africana studies whom the Trump administration sought to deport. Immigration officials had taken similar action against students at other universities whom they had accused of antisemitism.

Mr. Taal and other Cornell students shut down a campus career fair in 2024 that included weapons manufacturers. Facing removal by immigration authorities, Mr. Taal left the United States last year.

The school says that its policies surrounding demonstrations was enacted to combat “harassment, intimidation, shutting down events and threats of violence.”

Dr. Kotlikoff, who is a veterinarian, was appointed president of Cornell in March 2025 after an eight-month interim appointment. He had been the university’s provost from 2015 to 2024.

Thursday’s roughly two-hour event was an installment in an ongoing Israel-Palestine debate series and began ordinarily enough, with Dr. Kotlikoff introducing the discussion, which featured Norman Finkelstein, an author and political scientist.

Dr. Finkelstein’s remarks centered around Israel’s response to the Oct. 7, 2023, attacks. Pro-Palestinian and pro-Israel students also debated over the university’s policies on free speech and expression.

As he was leaving Cornell’s Goldwin Smith Hall, where the debate took place, Mr. Vallecillo and another student, Sophia Arnold, also a senior, asked Dr. Kotlikoff how the university could be reporting some students for misconduct while also deciding the outcome of the disciplinary actions against them.

In one of the videos that were provided to The New York Times by the students, Dr. Kotlikoff said that the university “has the responsibility and the accountability to make sure everyone in this community is protected.”

In an interview, Mr. Athas, who is a junior, said that Dr. Kotlikoff had not given him enough warning that he was backing up. He was unsatisfied with the president’s responses to their questions.

“We want to see the reversal of these draconian policies,” Mr. Athas said.

Stephanie Saul contributed reporting.