(CNN)Children and teens in the United States now get more than two-thirds of their calories from ultra-processed foods, an analysis of almost two decades worth of data has found.
Ultra-processed foods -- such as frozen pizza, microwave meals, packaged snacks and desserts -- accounted for 67% of calories consumed in 2018, up from 61% in 1999, according to research published in the medical journal JAMA Tuesday. The study analyzed the diet of 33,795 children and adolescents nationwide.
While industrial processing can keep food fresher longer and allow some foods to be fortified with vitamins, it modifies food to change its consistency, taste and color to make it more palatable, cheap and convenient -- using processes that aren't used in home-cooked meals. They are also aggressively marketed by the food industry.
"Some whole grain breads and dairy foods are ultra-processed, and they're healthier than other ultra-processed foods," said senior author Fang Fang Zhang, a nutrition and cancer epidemiologist at the Friedman School of Nutrition Science and Policy at Tufts University in Boston.
"But many ultra-processed foods are less healthy, with more sugar and salt, and less fiber, than unprocessed and minimally processed foods, and the increase in their consumption by children and teenagers is concerning."
The information on children's diets used in the study was collected annually by trained interviewers who asked the children or an adult acting on their behalf to detail what they had eaten in the preceding 24 hours. The information was gathered as part of the National Health and Nutrition Examination Survey.
Between 1999 and 2018, the proportion of healthier unprocessed or minimally processed foods decreased from 28.8% to 23.5% of consumed calories, the study found.