For the past two decades, Kevin Hall, a nutrition and metabolism scientist at the National Institutes of Health, has devoted his career to studying how people’s diets affect their health. He has led some of the world’s most important research on ultraprocessed foods, including one study that demonstrated, for the first time, that they caused people to overeat. This linked ultraprocessed foods to chronic conditions like Type 2 diabetes and obesity.
Dr. Hall had planned to keep doing this work for many years — and hoped it might accelerate under the health secretary, Robert F. Kennedy Jr., who has said that fixing the nation’s food supply is a priority. But now, at 54, he is retiring early.
In an interview with The New York Times, Dr. Hall said his decision was driven in part by several instances in which federal officials censored his work. In one, he said he was barred from speaking freely with reporters about a study that might have been seen as contradicting Mr. Kennedy’s stance on the addictive nature of ultraprocessed foods, which include products like chicken nuggets, hot dogs, packaged cookies and chips.
“We experienced what amounts to censorship and controlling of the reporting of our science,” Dr. Hall said, adding that he was worried that if he stayed, officials might also interfere with the design and execution of his studies. “That would make me hate my job every day,” he added.
Outside health experts said that Dr. Hall’s retirement is a setback for diet and chronic disease research.
“It’s a sad day when one of the most prominent nutrition researchers at N.I.H. feels forced to leave a job that he loves in an area that he’s having major public impact,” said Dr. Dariush Mozaffarian, the director of the Food Is Medicine Institute at Tufts University.
Scientists have been raising concerns for months that the Trump administration’s attacks on science, along with funding cuts, would lead to a loss of talent in federal health agencies and disrupt important medical research.
It’s still unclear if, or how, the new administration will invest in gold standard nutrition science, Dr. Mozaffarian said. Dr. Hall’s departure, he added, is not a positive first sign.
Censorship Was a ‘Huge Red Flag’
When Mr. Kennedy took over the Department of Health and Human Services, he pledged “radical transparency” of scientific information.
That commitment, Dr. Hall said, has not matched his experiences.
In February, Dr. Hall said that N.I.H. officials told him he couldn’t be listed as an author on a yet-to-be-published scientific review on ultraprocessed foods that he co-wrote with a group of university scientists. This was because the review included language about “health equity” (it acknowledged that some people in the United States don’t have access to healthy food). This discussion may not have aligned with President Trump’s views on diversity, equity and inclusion. If Dr. Hall wanted to stay on the paper, they said, that section would need to be modified. Dr. Hall removed his name — a first in his career as a government scientist.
It “is just infuriating” that Dr. Hall had to remove himself from the list of authors, said Christopher Gardner, a professor of medicine at Stanford University who was one of the scientists who led the review.
In March, Dr. Hall and his colleagues published a study that hinted that ultraprocessed foods were not addictive in the same way as some drugs.
When The Times requested a phone interview with Dr. Hall to discuss the study, the N.I.H. denied the request. Several days later, the agency allowed him to answer questions, but only in writing. Dr. Hall said that his responses, which had been sent through an N.I.H. press office, had been edited without his approval in a way that emphasized the study’s limitations and downplayed its significance.
To have federal officials interfere with how the study was portrayed to a news outlet was “galling” and “a huge red flag,” Dr. Hall said.
At the end of March, Dr. Hall emailed Mr. Kennedy and Dr. Jay Bhattacharya, the director of the N.I.H., expressing his concerns about the censorship and informing them that he was considering leaving his post. He also described how his research had been “hobbled” in recent months because of spending and hiring freezes that made it difficult to bring on research assistants and to buy food and other supplies for his clinical trials.
“The future of our studies seems bleak,” he wrote in the email. Mr. Kennedy and Dr. Bhattacharya have not responded.
The New York Times reached out to the Department of Health and Human Services and the National Institutes of Health for comment. They did not immediately respond to our request.
After publication, an H.H.S. spokesperson responded by writing, in part, that “N.I.H. scientists have, and will, continue to conduct interviews regarding their research through written responses or other means. We remain committed to promoting gold-standard research and advancing public health priorities.”
Federal officials have previously said that funding cuts and layoffs at health agencies reflect the priorities of H.H.S. and the Trump administration’s demand to downsize the government. (N.I.H. investigators were allowed to resume hiring research assistants last week, Dr. Hall said.)
Two Decades of Research, Interrupted
During his 21 years as an N.I.H. researcher, Dr. Hall has had a knack for identifying some of the biggest questions and controversies in nutrition science and designing experiments to settle them.
In a study published in 2011, for example, his team debunked a long-held belief that if you simply cut 500 calories from your diet each day, you could lose a pound of body weight each week. His research on the contestants from the reality show “The Biggest Loser” helped to explain why they often regained weight after it ended.
In 2019, Dr. Hall published the first clinical trial of ultraprocessed foods, which found that participants on an ultraprocessed diet consumed about 500 more calories per day and gained weight. They lost weight when they were on an unprocessed diet that included foods like grilled chicken, steamed broccoli and pasta.
This last study was “transformational,” said Jerold Mande, an adjunct professor of nutrition at the Harvard T.H. Chan School of Public Health and a former food policymaker who has served under Republican and Democratic administrations. It was the first to clearly show how ultraprocessed foods could cause obesity, he said.
In 2022, Dr. Hall began testing one of the biggest questions in nutrition research: What is it, exactly, that makes ultraprocessed foods so easy to overeat? Those results are expected this summer; and he said he is committed to publishing them, even after his departure.
Dr. Hall had hoped that with the growing concern over diet and chronic diseases on both sides of the aisle, he might be able to conduct larger nutrition trials more quickly.
It would be a “dream” to someday return to the N.I.H. to conduct that kind of research, he said. And if given the chance, he added, he would make sure the science is unbiased and “designed in a way to get the important answers that the American public deserves.”