Diet and the brain: more ultraprocessed food, more silent MRI changes, same test scores

If you grabbed a packaged snack this morning, there is no need to panic. A new study on diet and the brain found that people who ate the most ultraprocessed food had more silent changes on brain scans. Their memory and thinking test results, though, looked the same as everyone else’s.

Ultraprocessed foods are things like packaged snacks, sugary drinks and ready meals. Trading some of them for whole foods is a simple move, and this study gives you one more reason to try it.

How the study worked

Researchers in Canada looked at 8783 adults aged 35 to 69 who did not have heart disease. Each person filled out a detailed food questionnaire, had their body fat measured and got a brain MRI scan. The results were published Oct. 1, 2026, in JAMA Network Open. The study is a snapshot taken at one point in time, so it cannot show which came first, and the brain findings changed depending on how ultraprocessed food was defined.

What they found

The team compared the quarter of people who ate the most ultraprocessed food with the quarter who ate the least. The biggest eaters had:

• More body fat. About 2 percentage points higher, or 1.7 to be exact.
• More fat around the belly. Deep belly fat, the kind that sits around the organs, was greater.
• No difference in liver fat. The two groups looked alike here.
• More silent brain changes. The odds of showing signs of vascular brain injury on MRI were 1.40 times higher.
• No difference in thinking tests. Scores on two standard tests of memory and mental speed were not meaningfully different.

That last point is the reassuring part. Whatever the scans picked up, it was not showing up as worse day-to-day thinking in this group.

What is silent brain injury?

“Vascular brain injury” means small areas of damage to the brain’s tiny blood vessels. Doctors call it silent because it does not cause obvious symptoms. It shows up on a scan, not in how you feel.

These changes have been linked to stroke and dementia later in life. That is why researchers care about finding them in midlife. The same habits that are hard on the arteries of the heart can also be hard on the small vessels in the brain. Body fat, especially around the belly, may be part of the link, since it is tied to high blood pressure and inflammation.

The study shows that these things go together. It does not prove that ultraprocessed food caused the changes. Longer studies that follow people over time are needed to sort that out.

What you can do today

You do not have to overhaul your kitchen. Pick one ultraprocessed snack you eat often and swap it this week for a whole-food option, such as an apple, a handful of nuts or plain yogurt with fruit. Then notice whether you actually miss the old one. If the swap feels easy, add another next week.