Summary:
A controlled feeding and neuroimaging study from Virginia Tech finds that industrial food processing changes human metabolism and alters brain reward circuits independently of measured nutrient content. Published in Nature Metabolism, the trial compared meals matched within 1% for calories, carbohydrates, fats, proteins, fiber, water, and salt.
Although the meals were essentially identical by nutrition label, ultraprocessed foods produced markedly larger insulin surges, shifted how the body burned carbohydrates, and changed activation in the ventral striatum and nucleus accumbens when participants viewed food cues during fMRI scans.
Key Facts:
- Identical nutrients, different metabolic responses: In healthy adults eating meals matched to within 1% for calories, macronutrients, sodium, and water, ultraprocessed foods caused substantially higher insulin spikes and a longer elevation of blood glucose compared with minimally processed whole foods.
- Brain reward circuitry is affected: Differences in post-meal carbohydrate oxidation correlated with distinct neural activation in the ventral striatum and nucleus accumbens—central nodes of the brain’s reward and motivation network—when participants viewed images of foods during fMRI scans.
- Processing matters beyond macronutrient totals: The results provide direct biological evidence that industrial processing and breakdown of the natural food matrix can disrupt metabolic regulation and brain signaling through mechanisms separate from calories and macronutrient composition.
Source: Virginia Tech / Fralin Biomedical Research Institute at VTC
Background: For decades, nutritional science and public dietary guidelines have assumed that two meals with the same amounts of calories, carbohydrates, fats, and proteins would produce similar biological effects on metabolism and blood sugar control. Yet population studies tell a different story: diets high in ultraprocessed foods (UPFs)—which make up a large share of daily calories in many countries—are consistently linked to higher rates of type 2 diabetes, cardiovascular disease, obesity, and mood disorders.
A central debate among researchers has been whether UPFs are harmful mainly because they tend to be high in added sugars, saturated fats, and salt and low in fiber, or whether the industrial processing itself—altering the food’s structure and chemical makeup—induces unique physiological effects. The new randomized, controlled crossover study from the Fralin Biomedical Research Institute at VTC addresses that question directly.
Published in Nature Metabolism, the study shows that when ultraprocessed and minimally processed meals are matched within 1% for every major nutritional variable, the ultraprocessed option still provoked stronger insulin responses and changed neural signaling in brain circuits that control motivation and reward.
“Population-level data link greater UPF intake to worse health outcomes—obesity, cardiac events, diabetes, and even some mental health measures,” said senior author Alex DiFeliceantonio, Ph.D., associate professor at the Fralin Biomedical Research Institute and the Department of Human Nutrition, Foods, and Exercise at Virginia Tech. “We asked whether processing itself, independent of sugar, fat, or fiber differences, produces a different metabolic and neural outcome.”
Metabolic Chamber Testing: The 1% Nutritional Match
To isolate processing from nutrient content, researchers recruited 57 healthy adults aged 18 to 45. Thirty-two participants completed both metabolic chamber assessments and fMRI brain scans. Each volunteer consumed two distinct 300‑calorie test meals, given in randomized order at least three days apart after an overnight fast. Meals followed the NOVA classification system:
- Highly processed meal (NOVA 4): Items such as a peanut butter and jelly sandwich, commercial deli turkey, processed vegetable chips, a cookie, breakfast cereal, instant mashed potatoes, and water.
- Minimally processed meal (NOVA 1): Fresh sliced banana, dried unsweetened cranberries, whole cheese, and a hard‑boiled egg.
“These two meals are matched within 1 percent of carbohydrates, fat, proteins, calories, water, and salt,” said first author Zach Hutelin, who led the study during his doctoral training. “On paper they would be practically identical.”
Participants ate each meal within a 10‑minute window inside an airtight metabolic chamber that measured whole‑body energy expenditure and respiratory exchange ratios in real time. Blood samples were taken immediately after consumption and six more times over the next three hours.
The metabolic responses diverged quickly. The ultraprocessed meal produced much higher insulin levels and left blood glucose slightly elevated for longer. Although the body expended more total energy processing the ultraprocessed food, participants oxidized significantly less carbohydrate for fuel after that meal compared with the whole‑food option.
Neural Shifts in Reward and Motivation Circuits
Because post‑ingestive nutrient signals constantly communicate with the brain via the gut‑brain axis, the team examined whether these metabolic differences altered neural circuits that shape eating behavior. During separate fMRI sessions, participants viewed images of the nutritionally matched foods and rated their willingness to pay for each item.
Neuroimaging showed distinct activity shifts in the ventral striatum and nucleus accumbens—key structures in the dopaminergic mesolimbic reward system involved in reinforcement learning, incentive salience, and craving. The extent to which an individual’s carbohydrate oxidation changed after the ultraprocessed meal predicted the magnitude of neural responsiveness in these reward hubs when viewing food images. Participants did not report a conscious preference for the ultraprocessed items, yet their reward circuits registered the metabolic differences at an unconscious, neurobiological level.
“A major question has been whether associations between UPF consumption and poor health stem from nutrient composition or from processing itself,” commented Carlos A. Monteiro, M.D., Ph.D., professor of public health and creator of the NOVA classification system. “This study offers a novel contribution by tying post‑ingestive metabolic shifts to changes in brain reward circuitry.”
Deconstructing the Food Matrix
The authors stress that the trial used a single 300‑calorie meal in young, healthy volunteers, so larger studies are needed to determine cumulative effects from bigger meals, prolonged feeding, and populations with existing metabolic conditions. Future research will aim to pinpoint which aspects of industrial processing drive the metabolic‑neural decoupling—whether it is disruption of the natural cellular food matrix, faster gut transit and absorption, or specific additives and emulsifiers used in commercial formulations.
“Our next steps will examine particular processing steps and additives that may cause different metabolic responses,” DiFeliceantonio said.
Funding: The research was supported by a National Institutes of Health grant from the National Institute of Diabetes and Digestive and Kidney Diseases and by a National Science Foundation graduate research fellowship.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by staff.
About this neuroscience and diet research:
- Media Contact: Leigh Anne Kelley
- Source: Virginia Tech
- Image Credit: Image credited to Neuroscience News
- Original Research (Open Access): Nature Metabolism (Oct 5, 2026). “Metabolic and neural responses to ultraprocessed foods: a randomized, controlled, crossover study.” Authors: Zach Hutelin, Monica Ahrens, Mary Elizabeth Baugh, Emmanuel Nartey, Delbert L. Herald III, Alexandra L. Hanlon & Alexandra G. DiFeliceantonio.
- DOI: 10.1038/s42255-026-01619-4
Abstract
Metabolic and neural responses to ultraprocessed foods: a randomized, controlled, crossover study
Global dietary patterns have shifted toward greater consumption of ultraprocessed foods (UPFs), which are associated with increased disease burden. One mechanism proposed to link UPF consumption with metabolic disease is altered post‑ingestive responses compared with nutritionally similar foods.
This randomized crossover trial tested the effects of food processing on post‑ingestive metabolism and brain response in 57 healthy‑weight adults who consumed a nutritionally matched UPF or non‑UPF meal. Despite close nutritional matching, UPF meals produced greater insulinaemic and energetic responses and reduced carbohydrate oxidation relative to non‑UPF meals. Differences in peak carbohydrate oxidation were associated with striatal activation in response to food cues. Although subjective food valuation did not differ between conditions, brain responses correlated with valuation were positive for non‑UPF but negative for UPF in the visual cortex and striatum. These findings suggest that food processing influences post‑ingestive metabolic and neural responses through mechanisms beyond calories and macronutrients alone.
