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A Virginia Tech study of healthy adults found that meals matched for calories and key nutrients produced different metabolic responses depending on processing. Brain scans also showed processing-related differences in reward-system responses to food pictures, though participants did not report valuing either food category more.
Virginia Tech researchers have found that minimally processed and ultraprocessed meals matched for calories and key nutrients prompted different metabolic responses in healthy adults, alongside differences in brain activity when participants viewed food images. The study, published this month in Nature Metabolism, suggests processing itself may be associated with how the body and brain respond to food, although it does not establish that processing causes long-term disease or overeating.
The study included 57 healthy adults ages 18 to 45. Each participant ate both types of meal in separate sessions at least three days apart, allowing researchers to compare responses within the same person. The test meals contained 300 calories and were matched within 1 percent for carbohydrates, fats, protein, water, salt and weight.
After an overnight fast, participants ate a meal during a metabolic test. Researchers took blood samples after eating and measured metabolism over the following three hours. The ultraprocessed meal prompted a higher insulin response, and blood sugar remained somewhat higher for somewhat longer, according to the researchers. Participants also expended more energy and burned less carbohydrate for fuel after that meal. The study did not report that these short-term responses were diagnoses or evidence of lasting harm.
On a separate day, participants viewed food pictures during functional MRI scans. Thirty-two participants completed both the brain-imaging and metabolic sessions. Researchers reported differences in activity in the ventral striatum and nucleus accumbens, brain regions involved in learning, motivation and reward. Those brain responses were linked to differences in how participants burned carbohydrates after the meals. Participants did not say they would pay more for either category of food.
Processing May Affect More Than Nutrients
The findings matter because they suggest that a food’s measured nutrient profile may not fully predict the body’s immediate response to it. Researchers often compare foods by calories and macronutrients; this experiment indicates that processing may also be relevant to metabolic and brain responses, even when those measured features are closely matched.
The results may help researchers investigate possible mechanisms behind population-level associations between ultraprocessed-food consumption and health outcomes. Associate Professor Alex DiFeliceantonio said people who consume large amounts of these foods have higher rates of obesity, cardiac events, Type 2 diabetes and some mental-health measures in population data. Those associations do not show that processing alone causes the outcomes. The present study measured short-term responses to meals, not disease risk over time.
Ultraprocessed foods account for more than half of the average American’s daily calories, according to the source report. The study offers a reason to examine how processing relates to eating and metabolism, but it does not provide a basis for claiming that all ultraprocessed foods have the same effects or that individuals should make medical decisions from these results.
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How Researchers Matched the Meals
Many ultraprocessed foods are high in fat and sugar and low in fiber and protein, which can complicate efforts to isolate the role of processing itself. The Virginia Tech team designed the comparison to hold key nutritional measures close to equal. It classified foods using the Nova scale, which groups foods by level of industrial processing.
The ultraprocessed meal included portions of a peanut butter and jelly sandwich, deli turkey, vegetable chips, a cookie, cereal, instant mashed potatoes and water. The minimally processed meal consisted of banana, dried cranberries, cheese and egg. The researchers described the meals as nearly identical on nutritional labels, while differing in processing level.
Study first author Zach Hutelin conducted the work as part of his doctoral research at Virginia Tech. The metabolic chamber, an airtight room used to measure energy expenditure, and repeated blood tests let the team track immediate responses after eating. Brain imaging took place separately, using food photographs that included items served in the meal tests.
“If you look at that population-level data, people who consume large amounts of ultraprocessed foods have higher rates of poor health outcomes — obesity, cardiac events, Type 2 diabetes, and even some metrics of mental health.”
— Alex DiFeliceantonio, associate professor at the Fralin Biomedical Research Institute at VTC
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What the Short-Term Tests Cannot Show
The experiment recorded responses after one 300-calorie meal and tracked metabolism for three hours. It cannot determine whether repeated exposure produces lasting metabolic changes, affects body weight, or causes diabetes or other health conditions. The study also does not identify which features of processing might explain the differences.
The brain-imaging results show associations between metabolic differences and activity in reward-related regions while participants viewed food images. They do not prove that the brain responses lead people to eat more. Participants reported no greater willingness to pay for either type of food, and the researchers did not establish that the results apply to other age groups, people with health conditions, or every food in either processing category.
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Further Tests Must Explain the Differences
The findings point to further research on how processing relates to metabolism and responses to food cues, and on whether short-term differences persist under repeated or longer-term dietary conditions. The study report does not specify a date for a follow-up study or describe a planned clinical trial.
For now, the confirmed result is limited to the tested meals and participants: meals closely matched on several nutritional measures were followed by different metabolic responses, and brain activity related to food cues differed in a subset of participants. Whether those patterns help explain overconsumption or long-term health associations remains an open research question.
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Key Questions
What did the study find?
In healthy adults, a 300-calorie ultraprocessed meal and a minimally processed meal matched closely for measured nutrients were followed by different metabolic responses. Researchers also reported differences in brain activity while participants viewed food images.
Were the meals nutritionally identical?
They were not literally identical, but researchers said they were matched within 1 percent for calories, carbohydrates, fat, protein, water and salt. The foods and their level of processing differed.
Does the study prove ultraprocessed foods cause diabetes?
No. The study measured short-term responses after a meal; it did not track participants over time or test whether the meals caused disease. The researchers cited broader population associations, which are not proof of causation.
Did participants prefer ultraprocessed foods?
Participants did not report that they would pay more for either the ultraprocessed or minimally processed foods. The study found differences in brain responses to food pictures, but did not show that participants preferred one category.
Source: hn
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