Unhealthy ultra-processed foods have wormed their way into American kitchens, likely harming people's health for decades, a new study warns.

More than half of the calories adults eat at home now come from ultra-processed foods, which contain high levels of sugar, salt, fat and other additives, and have been linked to heart disease, obesity and Type 2 diabetes.

Folks typically consider ultra-processed food to be either fast food or junk food, but this heavily processed fare even includes options that might seem healthy at first, said lead researcher Julia Wolfson, an associate professor at the Johns Hopkins Bloomberg School of Public Health in Baltimore.

“The perception can be that ‘junk food’ and ultra-processed foods are equivalent,” Wolfson said in a news release from the university.

“Yet ultra-processed foods encompass many more products than just junk food or fast food, including most of the foods in the grocery store,” Wolfson added. “The proliferation and ubiquity of ultra-processed foods on grocery store shelves is changing what we are eating when we make meals at home.”

For the study, researchers analyzed data from annual health and nutrition surveys conducted by the U.S. Centers for Disease Control and Prevention between 2003 and 2018.

The research team used their answers to sort Americans’ daily diets into one of four groups — unprocessed or minimally processed foods, processed ingredients used during food preparation, processed foods and ultra-processed foods.

Foods containing artificial ingredients and colors were categorized as ultra-processed. These can include ice cream, deli meat, hot dogs, snack chips, breakfast cereals, fizzy drinks, frozen dinners and packaged soups.

On the other hand, minimally processed foods included fruits, vegetables and other whole foods that were either frozen or preserved fresh without additional salt or other ingredients.

Overall, ultra-processed foods comprised more than half of all calories consumed at home, rising from 51% in 2003 to 54% in 2018.

During that period, ultra-processed food intake dipped below 50% for only two groups — Hispanics and higher-income households.

Even then, the proportion of ultra-processed food never fell below 49% for the well-to-do or 47% among Hispanic people.

Worse, the proportion of total calories from healthy minimally processed foods fell during the study period, from 33% in 2003 to 29% in 2018.

The new study was published recently in the Journal of Nutrition.

Ultra-processed foods tend to be tempting even for people who like to cook, researchers said. They are easier and faster to prepare, and they often cost less and are more shelf-stable that scratch ingredients.

“We need strategies to help people choose less processed foods and avoid unhealthy ultra-processed foods for foods purchased for both at-home and away-from-home consumption,” Wolfson said. “Additionally, strong nutrition labels warning of high ultra-processed food content may be warranted.”