As a nutrition scientist, I was thrilled when I heard that the federal government was set to publish a definition of ultraprocessed foods this month. As many legislators have told me, the lack of a standardized definition is the biggest barrier to regulating ultraprocessed foods — like ice cream, soda and cookies — which make up more than half our diets and are linked to Type 2 diabetes, heart disease and dementia. A federal definition would create the foundation for policy that could reshape Americans’ diets and health.

Releasing the definition would have been a major win for Health Secretary Robert F. Kennedy Jr.’s Make America Healthy Again movement — though many Americans could have applauded the move, whether or not they agreed with Mr. Kennedy’s broader agenda.

But instead of releasing the definition on the expected day, the government announced that it had been sent to the Office of Management and Budget for review. This can be either the last step before a policy becomes official or a public health purgatory where it stalls indefinitely. Given the food industry’s prior success at delaying rules at this stage, I worry that in this case it will be the latter.

Indeed, it appears the food industry was the culprit behind this last-minute change of plans. Bloomberg News reported that major food company executives argued to the White House that releasing a definition of ultraprocessed foods would confuse customers and increase grocery costs — a claim that is far from certain. The Consumer Brands Association, a top industry lobbying group, said in a written statement: “We are confident that this definition won’t move forward once the president is made aware of it and the disastrous consequences it will have on his affordability agenda.”

Just last year, we saw the food industry forestall regulations using a seemingly similar strategy. The U.S. Department of Agriculture was poised to issue tougher rules to reduce salmonella contamination in raw poultry — until meat industry groups asked President Trump to withdraw the proposal, claiming it would raise food prices. The U.S.D.A. complied a few months later.

These events showcase a unique tension between health agencies, Mr. Kennedy’s MAHA agenda and a president who favors industry deregulation. Mr. Kennedy has named ultraprocessed foods as a root driver of chronic illness and called for an overhaul of the American food system. He has promised multiple times, including on Joe Rogan’s podcast and in congressional testimony, that the federal government would release a definition of ultraprocessed foods, to be followed by policies like front-of-package labeling. Achieving those goals would require regulating the food industry, clashing with Mr. Trump’s anti-regulatory agenda and the administration’s steep staffing cuts to the Food and Drug Administration and the U.S.D.A., the agencies responsible for creating and putting into effect new food rules.

The food industry is using tactics here that are similar to those they have used for decades. Companies have aggressively lobbied to block states from creating their own definitions of ultraprocessed foods, calling instead for a national standard — no doubt because the industry knows federal enforcement is often slower and easier to influence. The industry is likely to bring lawsuits over any legal definition. In late July, an investigation by Lighthouse Reports found that since 2010, food companies have filed 239 lawsuits in six countries, including the United States, against policies like front-of-package labeling and restrictions on junk food marketing to children. The industry has spent some $1.15 billion over 23 years on federal lobbying — more than tobacco, alcohol or gambling — and donated major sums to campaigns on both sides of the aisle. These actions can create a chilling effect on policymakers, who may not want to alienate donors or deal with expensive legal fights.

The companies contend that singling out foods based on how much they are processed would lead to the government targeting some traditionally healthy products such as hummus, yogurt and bread. They would prefer it if instead regulations focused on the amount of sugar, salt or refined carbohydrates in foods — in which case, they could avoid penalties by making tweaks to existing food formulations, rather than creating entirely different products.

There are reasonable solutions to this conundrum. In May, an independent panel of food experts, which I co-chaired, recommended classifying ultraprocessed foods based on whether they contain industrial ingredients almost never found in a home kitchen — while carving out exemptions for foods like whole grain breads that meet strict nutritional criteria. This approach works because it identifies ultraprocessed foods using information already available on food packages, and — crucial for addressing industry arguments — allows for truly healthy products to be exempt from regulations that follow.

Right now, Big Food is stalling serious food reform through lobbying. But there is still hope that we can win the battle for our diets. Polling shows that a majority of Americans, Republicans and Democrats alike, support action on ultraprocessed foods, such as clearer front-of-package labels, restrictions on marketing to kids and reduced availability in schools. The MAHA movement has demonstrated the demand for better food standards. The federal government should finalize and publish a strong, science-based definition of ultraprocessed foods. Barring executive action, Congress should move to pass its own definition.

Such a move would be a critical first step toward improving American diets.

Lindsey Smith Taillie is a professor of nutrition at the University of North Carolina, Chapel Hill, and a director of the U.N.C. Global Food Research Program.

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