BOSTON (WHN) – Young adults between 18 and 21 years old consume more calories from ultra-processed foods, even when not feeling hungry, according to new research. This finding emerges from a controlled trial designed to isolate the impact of highly processed food on eating behavior in a vulnerable age group amidst rising rates of excess weight among adolescents and young adults.
An analysis published in The Lancet projects that by 2050, approximately one in three Americans aged 15 to 24 will meet the criteria for obesity. This condition elevates the risk of serious health problems.
While genetics and reduced physical activity contribute, diet plays a primary role. Ultra-processed foods, which constitute 55 to 65 percent of the diet for young adults in the U.S., have been linked to metabolic syndrome, poor cardiovascular health, and other adverse conditions in adolescents.
Younger Adults More Susceptible to Ultra-Processed Foods
Researchers at Virginia Tech aimed to clarify how diets high in ultra-processed foods affect individuals aged 18 to 25. They compared two distinct dietary regimens: one rich in ultra-processed items and another entirely devoid of them. Following two weeks on each diet, participants were presented with an all-you-can-eat meal to assess their subsequent food intake.
When analyzing the entire cohort, the researchers observed no significant overall increase in calories or food mass consumed at a buffet-style breakfast. However, a nuanced age-related pattern emerged. Participants aged 18 to 21 consumed more calories at the breakfast following the ultra-processed diet. Those aged 22 to 25 did not exhibit this caloric increase.
The results, scheduled for publication Nov. 19 in the journal Obesity, suggest that adolescents and very young adults may be particularly susceptible to the behavioral effects of ultra-processed foods.
“Although this was a short-term trial, if this increase in caloric intake persists over time, this could lead to weight gain in these young people,” said Brenda Davy, a senior author on the paper and professor in Virginia Tech’s Department of Human Nutrition, Foods, and Exercise. She emphasized the potential long-term implications.
Neuroscientist and co-author Alex DiFeliceantonio, an assistant professor with Virginia Tech’s Fralin Biomedical Research Institute at VTC, stated, “The younger age group took in more calories from ultra-processed foods, even when they weren’t hungry.” His research focuses on the mechanisms governing food choice.
Understanding this demographic is critical. Adolescence and young adulthood represent a significant developmental phase. It’s a period when individuals gain independence, solidifying eating habits that can influence long-term health trajectories and potentially elevate obesity risk.
Controlled Diets and the NOVA System
The Virginia Tech team recruited 27 men and women, aged 18 to 25, whose weight had been stable for at least six months. Over two weeks, each participant adhered to one of two controlled eating plans. These plans included laboratory-served breakfasts, with all other meals prepared in a metabolic kitchen.
One diet sourced 81 percent of its total calories from ultra-processed foods. The alternative diet contained no ultra-processed foods whatsoever. The researchers meticulously matched the nutrient profiles of both diets, ensuring participants received only the caloric intake necessary to maintain their stable weight.
“We very rigorously designed these diets to be matched on 22 characteristics, including macronutrients, fiber, added sugar, energy density, and also many vitamins and minerals,” Davy noted. She highlighted that prior studies had not achieved this level of dietary standardization.
Food classification relied on the NOVA system, developed in Brazil. NOVA groups foods based on their degree of processing. Unprocessed or minimally processed foods include items like fresh fruit or legumes. Processed culinary ingredients, such as oils and salt, form another category. Processed foods, like cheese or canned vegetables, combine these ingredients through basic methods.
Ultra-processed foods, conversely, are characterized by industrial processing and often contain additives uncommon in home cooking. Examples include soft drinks, flavored yogurts, and most pre-packaged snacks.
This crossover trial design meant each participant served as their own control. They followed one diet for two weeks, returned to their usual eating patterns for four weeks, and then switched to the alternate diet.
Buffet Breakfast and Post-Meal Snacking
Following each two-week dietary period, participants were invited to a breakfast buffet featuring both ultra-processed and non-ultra-processed options. They arrived after fasting and were provided with approximately 1,800 calories of food—four times the average American breakfast—to consume freely over 30 minutes.
To specifically investigate eating in the absence of hunger, participants then received a tray of snacks immediately after breakfast. For 15 minutes, they were asked to taste each snack, rating its pleasantness and familiarity. Afterward, they could choose to continue eating or simply rest.
Age Differentiates Eating Behavior
Across the entire study group, the diet type did not influence total calories or grams of food consumed at the buffet. The proportion of ultra-processed foods selected also remained consistent, irrespective of sex or body mass index (BMI).
The age stratification, however, revealed a significant divergence. The 18- to 21-year-old subgroup consumed more calories after the ultra-processed diet period. These younger participants also demonstrated a greater tendency to continue eating even when no longer hungry.
“Our adolescent participants had just consumed more in the buffet meal after the ultra-processed diet. Then, given the opportunity to snack when not hungry, they ate more yet again,” DiFeliceantonio observed. He added, “Snacking when not hungry is an important predictor of later weight gain in young people, and it seems ultra-processed food exposure increases this tendency in adolescents.”
Previous trials with adults that offered continuous access to ultra-processed foods showed increased daily intake and subsequent weight gain. The Virginia Tech study, by maintaining consistent daily calories and energy density between diets and assessing intake at a single meal, aimed to isolate the specific effect of food processing itself on energy consumption.
“Here, since everyone was weight stable, we can see the effect of processing alone,” DiFeliceantonio explained. This approach avoids the confounding factor of increased energy needs due to weight gain.
The researchers acknowledge limitations, including the study’s brief duration and its focus on a single meal. These factors may not fully capture the complexities of real-world eating patterns, where food availability is often continuous.
Future research, Davy suggests, could involve longer intervention periods, inclusion of younger participants, or provision of continuous food access to better simulate everyday conditions. Expanding the participant cohort would also provide a clearer understanding of how age influences responses to ultra-processed diets.
The application of tools such as brain imaging and biomarkers could further elucidate the biological mechanisms connecting ultra-processed food exposure to behavioral changes across developmental stages. This remains an active research focus for DiFeliceantonio and Davy.
This research received support from a grant from the National Institutes of Health.