Two Weeks of Ultra-Processed Food Didn't Dull Satiety Hormones

A small Dutch trial published online on September 24, 2026, in the European Journal of Nutrition reports that two 14-day diets of about 95% ultra-processed food (UPF) did not change young adults' gut satiety hormone responses to a fixed-calorie meal. Hunger and fullness ratings shifted slightly, and the authors call their work a preliminary comparison study.

Key Takeaways

• A secondary analysis published on September 24, 2026, found that two 14-day diets of about 95% ultra-processed food did not change satiety hormone responses (GLP-1, ghrelin, PYY and PP) to a fixed-calorie meal in young adults.
• Participants reported slightly higher hunger and lower fullness overall after the high-UPF diets, though no individual time point differed significantly.
• The trial covered two weeks per diet in young, normal-weight adults. It tested one proposed mechanism and does not show that UPF-heavy diets are harmless.
• The authors disclose industry funding and ties, including a public-private research partnership and senior-author support from several food companies.

What happened

On September 24, 2026, researchers from the Sensory Science and Eating Behavior Group at Wageningen University & Research in the Netherlands published a secondary analysis in the European Journal of Nutrition (doi:10.1007/s00394-026-04111-7; open-access full text on PMC). It asked whether moving from a diet low in ultra-processed foods to a high-UPF diet affects satiety responsiveness.

A total of 41 participants completed the full controlled-feeding study, registered as NCT06113146 on ClinicalTrials.gov. Satiety hormones were measured in the 32 participants who could have a cannula (mean age 27 +/- 2 years, mean BMI 23.6 +/- 2.3 kg/m2). Nine participants were not cannulated; subjective ratings and fasting hormones cover all 41.

Across blood samples collected from 10 minutes prior to 180 minutes following a fixed-calorie test meal, researchers tracked plasma concentrations of glucagon-like peptide-1 (GLP-1), ghrelin, pancreatic polypeptide (PP), and peptide YY (PYY).

What changed

The paper starts from the idea that "disrupted satiety signalling has been proposed as a possible mechanism driving high energy intakes associated with the consumption of ultra-processed foods." This trial tested that idea under controlled feeding. The authors report: "Satiety hormone responses to the fixed-calorie load did not differ between baseline and following 14-day high-UPF exposure (all, p > 0.05)."

Similarly, the researchers observed: "Within each diet period, fasting-state appetite ratings remained stable across days on both UPF diets." In their primary conclusion, the authors wrote: "Our results do not support the hypothesis that satiety responsiveness is disrupted following two 14-day periods of high-UPF diet exposure."

However, participants' self-reported feelings told a slightly different story. The paper reported: "A small but significant difference was observed in acute subjective satiety ratings for total area under the curves (AUCs), with higher hunger and lower fullness AUCs following the high-UPF diets compared with baseline-measurements, though no significant differences were observed at individual timepoints (all, p > 0.05)."

The paper also summarizes energy intakes from the trial's primary paper: about 2,044 kcal per day at habitual baseline (about 45% from UPFs), about 2,301 kcal per day on the Slow UPF diet and about 2,671 kcal per day on the Fast UPF diet. This secondary analysis did not test why intake differed; the role of eating rate is the subject of the primary paper.

Who is affected

The participants were young, normal-weight adults with an average BMI of 23.6 kg/m2 who habitually consumed low amounts of ultra-processed foods. The findings may not apply to children, older adults, or individuals living with obesity, insulin resistance, or metabolic syndrome.

The menus supplied about 95% of daily energy from ultra-processed foods. Both arms were high-UPF; they differed in food texture designed to change how fast people ate ("Slow UPF" and "Fast UPF"). Main meals were eaten at the Wageningen eating-behaviour laboratory, and the comparison for this analysis was a baseline measured during a 1-week run-in on participants' usual diet.

We did not identify the specific foods or brands on the menus, and the trial tested whole diets, not individual additives such as emulsifiers, gums or sweeteners. The results cannot be mapped onto any single product.

What it means for shoppers

This trial did not find changes in gut fullness hormones after two weeks on high-UPF diets. That is a null result for one proposed mechanism; it does not contradict studies linking UPF to weight gain through other routes. For the wider evidence, see Ultra-Processed Food Trials: Weight Gain Clear, Cause Less So.

The study's funding and interests are worth knowing. It was funded by the Dutch Top-Consortium for Knowledge and Innovation Agri & Food (TKI 22.150, project "Restructure"), which the paper calls a public-private partnership on precompetitive research on food texture, eating rate and energy intake. Senior author C.G. Forde declares research support from Ajinomoto, Ferrero (Somartec) and Tate and Lyle, and speaking fees from Ferrero, PepsiCo, General Mills and Mondelez, among other industry ties. Co-author M.P. Lasschuijt declares fees and travel support from Nestle Nutrition; the other authors declare none. The paper does not say whether funders or industry partners influenced the study design. For a related look at industry ties in this debate, see Study: Most Critics of the Nova UPF System Had Industry Ties.

On a label, the ingredient list and the Nutrition Facts panel remain the most direct way to see what a packaged food contains.

The background

The Wageningen study represents a secondary analysis of a randomized crossover intervention designed primarily to evaluate how texture-derived eating rates influence energy intake. The primary trial evaluated energy intake differences, while this secondary paper isolated postprandial hormone and appetite dynamics.

This trial tested the satiety-hormone idea directly by comparing hormone curves at baseline with curves measured after 14 days on each high-UPF diet. GLP-1, ghrelin, PYY and PP responses did not differ. The result applies to this setting and time frame; it does not settle what drives higher energy intake on UPF diets.

The authors list clear limitations. Baseline satiety was evaluated after a standard 7-day free-living diet; the authors acknowledged that a controlled 14-day baseline run-in would have been a more rigorous comparator. Additionally, the semi-residential laboratory setting may have influenced subjective appetite ratings. The authors characterized their work as a preliminary comparison study and cautioned that the subjective hunger and fullness AUC differences should be interpreted carefully. Effects beyond the two 14-day periods were not studied.

What to watch next

In the United States, the Food and Drug Administration (FDA) and the U.S. Department of Agriculture (USDA) are working on a uniform definition of ultra-processed foods, according to the FDA's Ultra-Processed Foods page.

Open questions include whether the results hold beyond two weeks, and in people with overweight, older adults or children.