Young Adults Show Age-Specific Response to Ultra-Processed Diets in New Controlled Study

In a tightly controlled two-week experiment, researchers uncovered a striking age-related difference in how ultra-processed foods influence eating behavior among 18- to 25-year-olds. The study, conducted wiht 27 participants, tested two distinct diets: one rich in ultra-processed items and another devoid of them, while keeping total calories and nutrient balance constant.

The ultra-processed diet provided about 81 percent of total calories, while the comparison diet contained no ultra-processed foods at all. After each two-week period, participants were handed a large breakfast buffet and asked to eat as much as they wished. The researchers then measured how much they ate and their desire to snack when not hungry.

Across the entire group,the diet type did not produce a clear shift in total calories or weight of food eaten at the buffet. However, when broken down by age, a notable pattern emerged: individuals aged 18 to 21 consumed more calories after the ultra-processed diet, whereas those aged 22 to 25 did not show this uptick. The younger group was also more prone to continue snacking even when they were not hungry.

Senior author Brenda Davy emphasized that, although heightening caloric intake in a brief trial could signal weight gain over time, the study’s short duration means longer research is needed to confirm long-term effects. “If this increase in caloric intake persists, it could contribute to weight gain in these young people,” she said. Co-author Alex DiFeliceantonio noted that the younger participants’ tendency to eat more after exposure to ultra-processed foods-even when not hungry-could be a predictor of future weight gain.

Researchers stressed that adolescence and early adulthood are critical windows for forming feeding habits. As independence increases, so does the potential for risky eating patterns that elevate obesity risk later in life.

How the study was designed

Participants, 27 men and women aged 18-25 with stable weight for at least six months, spent two weeks on each diet. The meals at the study site, including breakfast, were prepared in a controlled kitchen to ensure precise nutrient matching. The two diets were balanced for 22 characteristics, including macronutrients, fiber, energy density, and vitamins, so that the only major variable was the degree of food processing.

To classify foods, researchers used the NOVA system, which groups items by processing level. Unprocessed or minimally processed foods include fresh fruit and plain yogurt; ultra-processed foods cover items such as soft drinks, flavored yogurt, and most pre-packaged meals. Each participant acted as their own control by alternating between the two diets in a crossover design: two weeks on one diet, four-week washout, then two weeks on the other.

Study at a glance

Why this matters-and what stays relevant

The study isolates the effect of food processing itself on energy intake, independent of total daily calories. It builds on a growing body of research linking ultra-processed foods with higher risks of metabolic disturbance and weight gain, notably during formative years. While this trial is small and short, its age-specific signal provides a valuable clue about how dietary experiences in late adolescence and early adulthood may shape long-term health trajectories.

Looking ahead, experts say longer studies with larger, more diverse groups are needed. Future work could incorporate neurobiological measures and biomarkers to uncover how ultra-processed foods influence brain appetite signals and reward pathways across development.

Disclaimer: This research reflects feeding patterns observed in a controlled setting. It does not constitute medical advice. For personal nutrition guidance, consult a healthcare professional.

What comes next

Researchers advocate extending intervention periods, including younger participants, and simulating real-world food access to better gauge everyday implications. The goal is to translate these findings into practical strategies that help teens and young adults form healthier, sustainable eating habits.

Engage with us

What policy or community-based changes would you support to reduce reliance on ultra-processed foods among youths? Do you think schools or local programs should play a bigger role in shaping healthier eating habits?

Which moments from this study resonate most with your own experiences or observations about teen and young adult eating patterns?

Share your thoughts in the comments and help spark a broader conversation about nutrition, youth health, and long-term well-being.