Two meals can look almost identical on a nutrition label and still affect the body differently.
That’s the takeaway from a new Virginia Tech study that compared an ultraprocessed meal with a less processed meal containing nearly the same calories, carbohydrates, fat, protein, fiber, sodium and water.
The study, published in Nature Metabolism, found that the ultraprocessed meal triggered a larger insulin response and changed how the body used energy after eating. Researchers also found differences in brain activity when participants viewed pictures of ultraprocessed and less processed foods.
The findings suggest that food processing may matter in ways that calories and basic nutrients alone do not fully capture.
But there is an important limit: this was a small, short-term experiment. It did not show that ultraprocessed foods cause diabetes, weight gain or other chronic health problems.
Researchers recruited 57 healthy adults ages 18 to 45. Thirty-two took part in the metabolic portion of the study, eating both test meals on different days so researchers could compare how the same person responded to each one.
The two meals were designed to be closely matched nutritionally.
The less processed meal included foods such as egg, banana, dried cranberries and cheese. The ultraprocessed meal included small amounts of foods such as deli turkey, instant mashed potatoes, cereal, veggie chips, a cookie and a peanut butter and jelly sandwich.
“If these meals had a nutritional label, they would be practically identical,” said Zach Hutelin, the study’s first author.
After participants ate, researchers tracked blood sugar, insulin and energy use for several hours.
Blood sugar did not differ much overall between the two meals, but insulin did. The ultraprocessed meal led to a much larger insulin response.
Researchers also saw differences in how the body used carbohydrates and fat for fuel after the meals.
Those findings are interesting, but they do not mean the ultraprocessed meal caused metabolic disease. The study only measured what happened over a few hours after one meal.
Still, the results help address a long-running question in nutrition research.
Many studies have linked diets high in ultraprocessed foods with obesity, type 2 diabetes and other health problems. But those studies often cannot separate the effects of processing from other differences in the diet, such as more sugar, less fiber or more calories.
This study tried to hold many of those factors steady.
“We know that the majority of ultraprocessed foods are high in fat, they're high in sugar, they're low in fiber, and they're low in protein,” said senior author Alexandra DiFeliceantonio. “But if we artificially hold all of those things constant, is there something about the processing that leads to a different outcome?”
The answer from this study is: possibly.
Processing can change the physical structure of food and how quickly nutrients become available during digestion. Ultraprocessed foods also may contain more additives or different combinations of ingredients.
But this study cannot say which of those differences mattered most.
The researchers noted that even though the meals had similar amounts of protein, the protein came from different foods. The ultraprocessed meal also contained more additives. Either of those factors, or something else about the foods’ structure, could have contributed to the different responses.
Researchers also looked at how the brain reacted to food images.
Participants underwent brain scans while viewing pictures of ultraprocessed and less processed foods. The scans showed differences in areas involved in food cues and reward.
That sounds dramatic, but the actual behavior did not change in an obvious way. Participants were not willing to pay more for the ultraprocessed foods.
So the study does not show that ultraprocessed foods “hijack” the brain or make people crave them more.
Instead, it raises a more modest possibility: the way food is processed may affect the body after eating, and those changes may also influence how the brain responds to food cues.
More research is needed to know whether these short-term differences matter over months or years.
The participants in this study were also relatively young and healthy, so the results may not apply in the same way to older adults or people with obesity, diabetes or other health conditions.
The study does not provide a simple rule that every ultraprocessed food is unhealthy or that minimally processed foods are always better. What it does suggest is that a nutrition label may not tell the whole story. Two foods with nearly identical calories and nutrients can still be different in ways the body notices.
The research was supported by the National Institutes of Health and a National Science Foundation graduate research fellowship.