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Ultra-processed food and appetite in adults 18-25

In the first controlled-feeding trial in adults 18-25, the full sample showed no difference in test-meal intake after two weeks of ultra-processed food. Only the 18-21 group ate more — an exploratory result from 11 people at a single meal.

First controlled-feeding trial finds no overall effect

In the first controlled-feeding trial in adults aged 18-25, the full sample of 27 showed no difference in buffet intake between diets; an exploratory analysis found the 11 participants aged 18-21 ate more after the ultra-processed diet, and the 16 aged 22-25 did not.

What this means

Does ultra-processed food drive overeating more in younger adults? In the first controlled-feeding trial in 18-25-year-olds, the full sample of 27 showed no difference in test-meal intake between diets. An exploratory analysis found the 11 participants aged 18-21 ate more at an unrestricted breakfast — and again when not hungry — after the ultra-processed diet; the 16 aged 22-25 did not. The age result rests on 11 people and one meal in one US trial — it cannot show sustained overeating or weight change.

Two matched diets, one measured meal

In adults, controlled trials show that freely eating ultra-processed food raises daily intake and weight; whether age changes that response had never been tested under controlled conditions. This trial, from Virginia Tech, published online in Obesity on November 19, 2025, is the first in 18-25-year-olds.

Thirty-three healthy, weight-stable US adults aged 18-25 — none with obesity, none restrained eaters — were randomized; 27 were included in the analysis (17 women, 10 men). Each ate two 14-day diets in random order, four weeks apart: 81% versus 0% of calories from ultra-processed foods (NOVA classification), matched on 22 nutritional characteristics and similar in energy density, at weight-maintaining calories. Compliance was near 99%, corroborated by urinary biomarkers. After each diet came an unrestricted buffet breakfast, then a snack tray — a test of eating in the absence of hunger.

A null overall, a split by age

In the full sample, buffet intake did not differ between diets (all p>0.05). The authors label the age-interaction finding exploratory. It was significant (p<0.001, d=1.22): the 18-21-year-olds ate more after the ultra-processed diet (p=0.03, d=0.79); the 22-25-year-olds did not (p=0.09). On the snack tray the younger group again ate more after that diet (p=0.017, d=0.85), the older group did not; that interaction was a trend (p=0.057). Hunger ratings before the buffet did not differ between diets. Neither diet produced weight gain: participants lost about 0.4 kg (0.9 lb) on the ultra-processed diet and about 0.5 kg (1.1 lb) on the other — not significantly different.

What it can’t say yet

As proof of concept, the trial tests one meal, not the continuous access that raises intake and weight in adult trials. No appetite hormones were measured; palatability was matched only broadly; the sample was small and 82% White. Whether processing itself, or energy density and palatability, drives the effect remains debated; the authors list continuous access, younger teens and brain imaging as open questions. The NIH primarily funded the work (R21HD109722); the authors declare no conflicts of interest.

Terms explained

  • NOVA classification — sorts foods by degree and purpose of processing; “ultra-processed” is its top tier.
  • Eating in the absence of hunger — snacks offered after a full meal, measuring eating not driven by hunger.
  • Exploratory analysis — a result treated as a lead to check, not a firm conclusion.

Sources

  1. Primary source: Rego MLM, Leslie E, Schmall E, Capra BT, Hudson S, Ahrens ML, Katz B, Davy KP, Hedrick VE, DiFeliceantonio AG, Davy BM. “The Influence of Ultraprocessed Food Consumption on Energy Intake in Emerging Adulthood: A Controlled Feeding Trial.” Obesity 34(2):344-356, published online November 19, 2025. https://doi.org/10.1002/oby.70086 (doi:10.1002/oby.70086; PMID: 41255123; PMC12850616). Full-text access.
  2. Context (adult landmark trial): “Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake.” Cell Metabolism, 2019. https://doi.org/10.1016/j.cmet.2019.05.008 (PMID: 31105044). Full-text access; cited for the established adult finding only.
  3. Context (adult replication): “Ultra-processed foods cause weight gain and increased energy intake associated with reduced chewing frequency: A randomized, open-label, crossover study.” Diabetes, Obesity and Metabolism, 2024. https://doi.org/10.1111/dom.15922 (PMID: 39267249). Abstract-level access; cited for the established adult finding only.

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