Over the past 2 decades, childhood obesity has risen steadily. About 20% of youth aged 2 to 19 are now considered obese. Many societal trends have contributed to this rise, including reductions in physical activity and changes in diet.
Previous research has suggested that “ultra-processed” foods may directly contribute to weight gain. These foods contain ingredients rarely found in home cooking, such as high-fructose corn syrup, flavoring agents, and emulsifiers. Making them requires industrial methods, like high-pressure shaping and chemical alteration. Examples of ultra-processed foods include sodas and other sweetened drinks, candy, industrial breads and breakfast cereals, and ready-to-heat and -eat dishes found in the freezer section of the supermarket.
Researchers led by Dr. Fang Fang Zhang from Tufts University examined recent trends in ultra-processed food consumption among U.S. youth. They looked at data from the National Health and Nutrition Examination Survey, or NHANES, collected between 1999 and 2018. During those two decades, the survey recorded information on diet from almost 34,000 kids and young adults aged 2 to 19.
The team classified foods and beverages into four categories: unprocessed or minimally processed, processed culinary ingredients (such as plant oils), processed foods, and ultra-processed foods.
The researchers looked at changes in the proportion of calories coming from ultra-processed foods over the 20 years of the study. They also examined differences in these trends based on age, sex, race and ethnicity, and household education and income levels.
The study was funded in part by NIH’s National Institute on Minority Health and Health Disparities (NIMHD). Results were published on August 10, 2021, in JAMA.
Overall, the proportion of calories in youths’ diets that came from ultra-processed foods rose between 1999 to 2018, from about 61% to 67%. The proportion from whole, unprocessed foods dropped from almost 29% to 23.5% during the same time period.
The biggest jump in ultra-processed food consumption came from ready-to-heat and -eat dishes, which accounted for about 11% of daily calories in 2018, compared with 2% in 1999. The percentage of calories that came from sweets and sweet snacks also rose during the time period studied, from about 10% to almost 13%.
Consumption of sodas and other sugary drinks dropped during the years studied, from accounting for almost 11% of daily calories to around 5%. But overall, higher levels of ultra-processed foods meant a higher percentage of calories from added sugars and carbohydrates and lower levels of fiber, protein, and most vitamins.
These trends were observed for all ages, for boys and girls, and for all racial and ethnic groups. However, ultra-processed foods accounted for greater increases in calories for non-Hispanic Black and Mexican American youths compared with non-Hispanic White youths. No differences in consumption were seen based on household education or income levels.
“Some whole grain breads and dairy foods are ultra-processed, and they’re healthier than other ultra-processed foods. Processing can keep food fresher longer, allows for food fortification and enrichment, and enhances consumer convenience,” Zhang says. “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.”
