During the same two-decade period when the study data was collected, the consumption of unprocessed or minimally processed foods decreased to 23.5% from 28.8%, the study found.
The greatest increase in calories came from ready-to-eat or ready-to-heat meals such as pizza, sandwiches and hamburgers, rising to 11.2% of calories from 2.2%. Packaged sweet snacks and treats such as cakes and ice cream were a runner-up, which made up 12.9% of calorie consumption in 2018, compared to 10.6% in 1999.
When broken down by race and ethnicity, the growth in consumption of ultra-processed foods was significantly higher for Black, non-Hispanic youth, compared to white, non-Hispanic youths. The study also noted that Mexican American youths consumed ultra-processed foods at a persistently lower rate, which the researchers said may indicate more home cooking by Hispanic families.
The study also found that the education levels of parents or family income didn’t affect consumption of ultra-processed foods, suggesting that these types of foods are common in many households.
But the responsibility for tackling this problem shouldn’t fall only on parents, Zhang says.
While she would encourage parents and children to consider “replacing ultra-processed foods with minimally and unprocessed foods,” Zhang says changes at the policy level are needed “to achieve a broader and more sustainable impact.”
Take, for instance, consumption of soda. The consumption of sugar-sweetened beverages dropped to 5.3% from 10.8% of overall calories. The study’s researchers noted that the decline could be related to efforts such as soda taxes and raising awareness about the effects sugar has on youth health.
“We may have won this battle, at least partially for some sugary beverages,” Zhang says, “but we haven’t yet against ultra-processed foods.”
This widespread reliance on junk food is an increasing public health concern, as the obesity rate has been rising steadily among U.S. youths for the past two decades.
While the study’s authors said that the relationship between childhood obesity and ultra-processed foods is complex, they acknowledge that “cohort studies provide consistent evidence suggesting high intake of ultra-processed foods contribute to obesity in children and young adults.”
Indeed, a 2019 study by researchers at the National Institutes of Health found that a diet filled with ultra-processed foods encourages people to overeat and gain weight compared to diets that consist of whole or minimally processed foods.