By SmashMeals Editorial — 2026-09-29 — Health & Nutrition
The short answer
In 32 young adults, two 14-day diets providing about 95% of energy from ultra-processed foods produced a small overall shift toward higher hunger and lower fullness compared with baseline, but researchers did not find significant changes in GLP-1, ghrelin, PYY or pancreatic-polypeptide responses. The authors concluded the study did not support the hypothesis that short-term high-UPF exposure disrupts satiety responsiveness.
Key facts
- The study was a randomized crossover trial with 32 participants and two 14-day high-UPF diet periods.
- Participants were young adults with habitual low ultra-processed-food intake.
- Overall subjective hunger/fullness shifted slightly, but individual timepoints were not significantly different.
- Measured GLP-1, ghrelin, PYY and pancreatic-polypeptide responses did not significantly change.
- The trial does not show that ultra-processed foods are harmless or that processing never affects intake; it tested a specific short-term satiety mechanism.
KINGSPORT, Tenn., Sept. 29, 2026 — A new randomized crossover trial is a good example of why nutrition headlines need context. Researchers at Wageningen University tested whether short-term exposure to diets extremely high in ultra-processed foods would disrupt the body's satiety response.
The answer was not a simple yes. Participants reported a small overall shift toward more hunger and less fullness after the high-UPF periods, but measured satiety-hormone responses — including GLP-1 — did not significantly change.
What researchers actually did
The study included 32 young adults who normally ate relatively little ultra-processed food. Each participant completed two 14-day diets providing roughly 95% of energy from ultra-processed foods, with a 14-day washout between them. Researchers measured subjective appetite and blood concentrations of GLP-1, ghrelin, peptide YY and pancreatic polypeptide around a fixed-calorie meal.
What the study found — and did not find
Across the full measurement period, hunger was somewhat higher and fullness somewhat lower after the high-UPF diets than at baseline. But differences at individual timepoints were not significant, and the hormone responses did not significantly differ. The researchers concluded that their results did not support the hypothesis that two short high-UPF exposures disrupt satiety responsiveness.
That is narrower than saying ultra-processed foods have no health effects. The study tested one proposed mechanism, over a short period, in a small and relatively young sample.
Why this belongs in a meal-prep newsroom
Food marketing loves binary labels: clean or processed, good or bad, healthy or unhealthy. This trial is a reminder to look underneath those labels. Portion, ingredients, nutrition, texture, eating rate and the overall dietary pattern can all matter.
SmashMeals publishes meal-level nutrition information so customers can compare the food actually available this week. For related reading, see our GLP-1 nutrition research report and latest GLP-1 nutrition update.
Commentary, not medical advice
The SmashMeals perspective
The practical lesson for a prepared-food company is restraint: do not turn 'processed' versus 'unprocessed' into a simplistic health score. Shoppers deserve the actual portion, ingredients and nutrition information, while researchers keep testing which aspects of food processing, texture and eating rate matter.
Sources & experts referenced
Sources are included for verification. No expert listed here endorses SmashMeals.
- Satiety responsiveness following dietary exposure to ultra-processed foods differing in texture-derived eating rate — European Journal of Nutrition
Why it matters: Primary peer-reviewed randomized crossover trial published Sept. 24, 2026. - PubMed record: Satiety responsiveness following dietary exposure to ultra-processed foods — National Library of Medicine
Why it matters: Independent bibliographic record confirming study design, authors and publication details.