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In a small study published in Nature Metabolism, participants had different metabolic responses after eating highly processed and minimally processed meals matched on key nutritional measures. Brain scans also found differences in responses to food pictures, but participants did not report valuing one type of food more, and the study does not establish long-term health effects.
Virginia Tech researchers reported that meals with different levels of processing prompted distinct metabolic responses, even when the meals were matched on calories, carbohydrates, fat, protein, water, salt, and weight. In a study published this month in Nature Metabolism, highly processed meals were associated with a higher insulin response, greater energy expenditure, less carbohydrate use for fuel, and different brain responses to food images than minimally processed meals.
The study included 57 healthy adults ages 18 to 45. Participants ate both types of meal in separate sessions at least three days apart, allowing researchers to compare responses within the same person. The meals each contained 300 calories and were matched to within 1 percent on the reported nutritional measures. Researchers classified processing using the Nova scale.
For metabolic testing, participants fasted overnight and ate a meal in a controlled metabolic chamber. Researchers collected blood samples after eating and tracked responses for three hours, including insulin, energy expenditure, and carbohydrate oxidation. The highly processed meal included items such as a peanut butter and jelly sandwich, deli turkey, veggie chips, a cookie, cereal, and instant mashed potatoes. The minimally processed meal included banana, dried cranberries, cheese, and egg.
In a separate session, 32 participants completed brain imaging and metabolic testing. During functional MRI scans, they viewed pictures of foods and reported how much they would pay for them. The researchers found differences in activity in reward-related brain areas, including the ventral striatum and nucleus accumbens. Participants did not say they would pay more for either category of food.
Processing May Change More Than Nutrients
The findings suggest that processing level may be associated with bodily responses beyond what is captured by calories and the measured amounts of major nutrients. That matters because studies often explain responses to meals through their carbohydrate, fat, protein, and energy content. The reported differences raise a further research question: whether processing itself, or other features that accompany it, helps shape metabolism and brain responses.
Ultraprocessed foods account for more than half of the average American’s daily calories, according to the source report, and their share is rising in diets worldwide. Such foods are often designed to be convenient, affordable, accessible, and highly palatable. Researchers have linked diets high in these foods with poor health outcomes, but this experiment does not show that processing caused those outcomes. It offers a controlled comparison that may help guide investigation of possible mechanisms.
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A Controlled Meal Comparison
Many ultraprocessed foods differ from less processed foods in several ways at once: they can contain more sugar and fat and less fiber and protein. That makes it difficult to isolate the role of processing when comparing everyday diets. The Virginia Tech team asked whether responses would still differ when the meals were closely matched on selected nutritional measures.
Alex DiFeliceantonio, an associate professor at the Fralin Biomedical Research Institute at VTC whose lab led the study, said the researchers wanted to hold those factors constant. Zach Hutelin, the study’s first author and a doctoral researcher, said the meals were matched within 1 percent on the listed measures. The experiment was a short-term test of responses to specific meals, not a trial of long-term eating patterns or disease risk.
“The two meals are matched within 1 percent of carbs, fat, proteins, calories, water, and salt.”
— Zach Hutelin, study first author and Fralin Biomedical Research Institute researcher
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What the Short-Term Study Cannot Show
The experiment measured responses over hours after one 300-calorie meal; it did not test whether repeated exposure to these meals causes diabetes, heart disease, weight gain, or mental-health conditions. The source report does not provide enough information to determine how representative the participants were of the wider population, or whether the observed responses would be similar across age groups and health conditions.
Although the meals were matched on several measures, the report does not establish which aspect of processing produced the differences. Food structure, ingredients, or other features could contribute. The brain-imaging results show differences in responses to food pictures, but participants reported no difference in how much they would pay. The precise relationship between the metabolic and brain findings, and their significance for everyday food choices, remains under study.
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Further Tests Must Identify the Mechanism
The published findings point to follow-up research on how processing relates to metabolism and brain responses, and on which properties of foods might account for the observed differences. Longer studies would be needed to determine whether short-term responses persist with repeated eating and whether they affect health over time.
The available report does not specify a next study or give a timetable for further results. For now, the findings should be read as evidence of different short-term responses under the study’s test conditions, rather than proof that food processing alone causes long-term illness or overeating.
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Key Questions
What did the researchers find?
Participants showed different metabolic responses after highly processed and minimally processed meals matched on several nutritional measures. Researchers also observed differences in brain activity while participants viewed food pictures.
Were the meals nutritionally identical?
They were not described as identical in every respect. The researchers said the meals were matched within 1 percent for calories, carbohydrates, fat, protein, water, and salt, and the study also matched meal weight.
Does the study prove ultraprocessed foods cause disease?
No. It measured short-term responses to meals and did not test whether eating these foods over time causes disease. The researchers discussed population-level associations, which are distinct from proof of cause and effect.
Did participants prefer the highly processed foods?
Participants did not report being willing to pay more for either the highly processed or minimally processed foods. The brain scans nevertheless showed differences in responses to food cues.
Who took part in the research?
The full study included 57 healthy adults ages 18 to 45. Of those, 32 completed both the brain-imaging and metabolic sessions, according to the report.
Source: hn
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