Ultra-processed foods linked to changes in brain regions that control eating behavior, study finds

A new study published in npj Metabolic Health and Disease suggests that eating more ultra-processed foods may not only increase the risk of obesity and poor metabolic health, but could also be associated with structural changes in brain regions involved in regulating food intake and reward. Researchers found that these changes in the brain were linked to both higher body fat and markers of inflammation, indicating that ultra-processed foods may influence the brain through multiple biological pathways—not just through increased calorie consumption.

Ultra-processed foods, or UPFs, are heavily manufactured products that typically contain additives, preservatives, and ingredients not found in traditional home cooking. While previous studies have shown that UPFs contribute to overeating and weight gain, much less is known about why they lead to increased food intake and whether they directly affect the brain. The researchers behind this new study aimed to fill that gap by examining whether UPF consumption is associated with differences in brain structure, and whether these differences are explained by factors such as body fat, inflammation, and cholesterol levels.

“We were interested in the topic because there is no convincing evidence of how ultra-processed food (UPF) consumption is associated with brain structure in humans,” explained study author Filip Morys, a research associate at the Montreal Neurological Institute at McGill University.

“We also don’t know what causes those hypothesized associations – a lot of researchers claim that UPF consumption increases obesity and that this is the only path that leads to brain damage, but there is a possibility that there are other pathways, e.g. additives in UPFs could cause inflammation and negatively affect the brain.”

The researchers analyzed data from the UK Biobank, a large health study that has followed more than 500,000 participants over many years. For this specific analysis, they focused on around 33,000 people who had completed dietary surveys and undergone brain scans. Participants reported what they ate in multiple 24-hour dietary recalls, and researchers calculated the percentage of total calories that came from ultra-processed foods. On average, nearly half of the calories consumed by participants came from UPFs.

The team also gathered detailed health information from these participants, including their body mass index (a measure of body fat), waist-to-hip ratio, and visceral fat. They looked at blood markers such as cholesterol levels, inflammation (measured by C-reactive protein), blood sugar (HbA1c), and blood pressure. Finally, they analyzed high-resolution brain scans, focusing on areas of the brain involved in eating behavior, including the hypothalamus, nucleus accumbens, amygdala, and several white matter tracts.

The study found that higher UPF consumption was associated with a range of negative health indicators. People who ate more UPFs tended to have higher levels of body fat, more inflammation, worse blood sugar control, and lower levels of healthy cholesterol. They also consumed more sugar, saturated fat, and sodium.

But most strikingly, UPF intake was linked to structural differences in specific brain regions. For example, people who consumed more UPFs had signs of increased cellular density in the hypothalamus, which may reflect inflammation in this brain region. The hypothalamus plays a key role in regulating hunger and metabolism.

At the same time, participants showed signs of reduced cellular integrity in the nucleus accumbens, putamen, and pallidum—areas involved in reward and motivation, including food cravings and pleasure from eating. These findings suggest that UPF consumption may be related to both inflammation and degradation in the brain’s appetite and reward systems.

“What surprised us was how specific our findings were – brain structures that were associated with higher UPF consumption were the ones that are related to appetite and food intake regulation as well as reward,” Morys told PsyPost. “Once again, that could mean that UPF affects those regions which then leads to a higher UPF consumption.”

The researchers also conducted mediation analyses to understand whether the effects of UPFs on the brain were indirect—that is, whether they were explained by other health factors like inflammation or obesity. They found that some of the associations between UPF intake and brain structure were partially explained by body mass index and markers of inflammation such as C-reactive protein. For instance, the link between UPF consumption and changes in the nucleus accumbens appeared to be mediated by higher inflammation levels. Other brain changes, such as differences in the hypothalamus, were mediated by increased body fat.

Interestingly, not all brain effects were explained by obesity or inflammation. Some associations remained even after accounting for these factors, suggesting that other components of UPFs—such as additives, emulsifiers, or the combination of fats and carbohydrates—might have a direct influence on brain health. This aligns with findings from animal studies, which have shown that ingredients commonly found in UPFs can lead to inflammation and damage in the brain, independent of weight gain.

The study adds to a growing body of research suggesting that diets high in ultra-processed foods may trigger a cycle that reinforces overeating. “I think for an average person it should be important to know that UPF consumption can reshape our brain’s reward and homeostatic systems in a way that could further increase our UPF consumption,” Morys told PsyPost.

“We already know that UPFs are designed to make us overeat them – here we are showing what the mechanisms for this could be. There might be a vicious cycle happening here (but see caveat). An interesting fact is that some of the effects of UPFs on the brain are indeed because it leads to increased body fat, but there are also different mechanisms that could involve additives, etc.”

However, the authors caution that their findings are based on cross-sectional data, meaning they took a snapshot of each participant’s brain and diet at one point in time. Because of this, they cannot determine whether UPF consumption causes brain changes or whether people with different brain structures are more likely to eat UPFs. It’s also possible that the relationship is bidirectional, where brain changes and dietary habits influence each other over time.

“The caveat is that this is a cross-sectional study,” Morys explained. “This means that we cannot solve the problem of which comes first – brain changes or UPF consumption. Or perhaps, as we think, both happen reciprocally. But with this study, we can only hypothesize about the specific mechanisms.”

Future research is needed to test these findings in controlled experimental studies, and to explore which specific features of UPFs—such as calorie density, specific additives, or the blend of nutrients—are most responsible for these brain changes. Understanding this could help in developing healthier food alternatives and more effective strategies to reduce UPF consumption.

“We would be very interested in investigating which parts of food processing lead to the brain changes that we found,” Morys said. “Is it the fact that UPFs are higher in calories? Are those special additives? Other substances? Combination of carbohydrates and fat? We do not know this and it could help create healthier alternatives.”

The study, “Ultra-processed food consumption affects structural integrity of feeding-related brain regions independent of and via adiposity,” was authored by Filip Morys, Arsene Kanyamibwa, Daniel Fängström, Max Tweedale, Alexandre Pastor-Bernier, Houman Azizi, Lang Liu, Annette Horstmann, and Alain Dagher.