Fatty meals, fading memory

September 13, 2025

Eating junk food for only a few days may harm the brain’s memory and learning functions, a new study has warned. R e s e a rc h e rs at t h e University of North Carolina (UNC) found that just four days of consuming a high-fat diet, similar to cheeseburgers, fries and other fatty fast foods, can disrupt memory processes in the brain before any signs of weight gain or diabetes appear. The findings, published in the journal Neuron, show that fatty foods can have almost immediate effects on the hippocampus, the part of the brain that controls memory and cognitive skills.

The research identified a specific group of brain cells called CCK interneurons in the hippocampus that become overactive when exposed to a high-fat diet. This happens because the brain’s ability to absorb glucose, its main source of energy, is reduced. The abnormal activity of these neurons interferes with how the hippocampus p r o c e s s e s m e m o r y. Juan Song, professor of pharmacology at UNC School of Medicine and senior author of the study, said the results revealed an unexpected vulnerability.

“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 directly disrupted by short-term high-fat diet exposure,” she explained.“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,” she added.For the study, mice were fed a high-fat diet resembling Western junk food before being tested for memory and learning ability. Within just four days, the mice showed abnormal activity in CCK interneurons and a decline in memory performance.

The researchers also discovered that restoring glucose levels in the brain reversed the problem. Providing glucose calmed the overactive neurons and corrected memory issues in the mice. Further analysis revealed that a protein called PKM2, which regulates how cells use energy, plays a central role in the process. The findings suggest that targeting energy metabolism in the brain could help prevent memory problems linked to obesity and high-fat diets.The team also found that simple interventions such as intermittent fasting following periods of highfat intake were effective. Fasting normalised CCK interneuron activity and restored memory function in the mice, indicating that dietary adjustments could provide a practical way to protect brain health. The study highlights the possibility of developing e a rl y i n t e r ve n t i o n s , through diet or drugs, to prevent long-term memory loss and cognitive decline associated with obesity and poor nutrition.