We’ve all been guilty of overindulging in burgers, chips and fried food from time to time. But new research shows it could be harming not just your waistline, but your memory—and much sooner than you’d expect.

Researchers found that a high-fat diet—like burgers and fries—causes certain brain cells in the hippocampus, called CCK interneurons, to become overactive because the brain struggles to process glucose (sugar). This overactivity weakens memory function after just a few days of eating poorly.

The study, led by UNC School of Medicine’s Juan Song, PhD, principal investigator, professor of pharmacology, and Taylor Landry, PhD, first author, Department of Pharmacology, uncovered just how vulnerable these brain cells are.

“We knew that diet and metabolism could affect brain health, but we didn’t expect to find such a specific and vulnerable group of brain cells, CCK interneurons in the hippocampus, that were directly disrupted by short-term high-fat diet exposure,” Song said.

“What surprised us most was how quickly these cells changed their activity in response to reduced glucose availability, and how this shift alone was enough to impair memory.”

As part of the research, mice were placed on a high-fat diet resembling typical junk food. Shockingly, within just four days, their memory hub began to show disruption as CCK interneurons became abnormally active.

The finding highlights how quickly diet can interfere with memory, raising concerns about longer-term risks such as dementia and Alzheimer’s disease.

“This work highlights how what we eat can rapidly affect brain health and how early interventions, whether through fasting or medicine, could protect memory and lower the risk of long-term cognitive problems linked to obesity and metabolic disorders,” said Song.

“In the long run, such strategies could help reduce the growing burden of dementia and Alzheimer’s linked to metabolic disorders, offering more holistic care that addresses both body and brain.”

Looking ahead, the researchers want to see if these therapies can be applied to people and whether junk food diets play a direct role in Alzheimer’s disease. They’ll also explore everyday solutions—like eating patterns that keep brain glucose steady—as possible ways to protect memory.

It’s not only junk food that could be impacting our cognitive ability, with recent research suggesting that long-term insomnia could also accelerate memory decline and increase the risk of dementia.

Published in Neurology, the research shows that people living with chronic insomnia—defined as difficulty sleeping at least three nights a week for three months or longer—faced a 40 per cent higher risk of mild cognitive impairment or dementia compared with those who slept more soundly.

The study’s authors say that the difference is similar to adding an extra 3.5 years of ageing to the brain.

“Insomnia doesn’t just affect how you feel the next day—it may also impact your brain health over time,” said study author Diego Z. Carvalho, MD, of the Mayo Clinic in Rochester, Minnesota, and a member of the American Academy of Neurology.

“We saw faster decline in thinking skills and changes in the brain that suggest chronic insomnia could be an early warning sign or even a contributor to future cognitive problems.”

Researchers followed 2,750 older adults, average age 70, for nearly six years. Of these, 16 per cent had chronic insomnia. Each year, participants completed memory and thinking tests, and some also had brain scans.

By the end of the study, 14 per cent of people with insomnia had developed mild cognitive impairment or dementia, compared with 10 per cent of those without sleep problems. The risk remained even after adjusting for age, blood pressure, sleep medication use, and sleep apnea.

Together, these findings serve as a powerful reminder: what we eat and how well we sleep can rapidly affect not only how we feel day to day, but also the long-term health of our memory and brain.

IMPORTANT LEGAL INFO This article is of a general nature and FYI only, because it doesn’t take into account your personal health requirements or existing medical conditions. That means it’s not personalised health advice and shouldn’t be relied upon as if it is. Before making a health-related decision, you should work out if the info is appropriate for your situation and get professional medical advice.