Fast food can do this damage to brain within 4 days: Study reveals how to reverse it

The common consequences of a high-fat diet include weight gain. But the damage to one of the most important brain function can happen much sooner.

High-fat diet is generally thought to adversely impact weight and waistline. The harmful effects of a diet high in saturated fats, such as the usual fast food delicacies, like French fries, burgers, are commonly known to be detrimental to the heart, spiking bad cholesterol. But the consequences can reach deep into brain function, even memory.

A high-fat diet momentarily dulls one of your brain functions. (Freepik)

A study published by the UNC School of Medicine on September 11, 2025, highlighted that fast food can ‘alter’ the brain's memory circuit, just within a few days. Even more shocking? These changes happen even before the traditional effects like weight gain show up.

High-fat diet disturbs brain cells?

The study examined a brain region called ‘hippocampus' in mice. This region plays a very important role in both forming and storing memories. There's a type of neuron (brain cell) called a CCK interneuron. They help to regulate how memories are stored, formed and recalled. When the mice in the study were given to eat high-fat foods, this particular neuron became very overactive, just within a span of four days.

Why does this happen? The main reason is that the CCK interneuron becomes overactive because the brain didn’t have enough glucose, which is the main source of energy. Without fuel, the brain doesn’t work properly, and memory takes a hit. In the study, the mice had trouble remembering things before they gained weight. On a high-fat diet, the body processes the unhealthy fat, reducing how much glucose is available to the brain. The overactivity of the neuron made it a challenge for the mice to remember things.

How to reverse

Intermittent fasting is an eating pattern which involves periods of eating and fasting- based on time. It is one of the ways to reverse the consequences of high-fat diet. (Shutterstock)

So, in other words, even short-term consumption of high-fat junk foods affects memory, making it much weaker. But all hope is not lost, even if you have indulged in junk foods on cheat days out of temptation. There are strategies to reverse it, as the researchers highlighted, like intermittent fasting or adjusting the diet after a high-fat period, that also helped normalise neuron activity and rescued memory. This is a perfect example to also show how sensitive the brain is to what is on your plate.

Note to readers: This article is for informational purposes only and not a substitute for professional medical advice. Always seek the advice of your doctor with any questions about a medical condition.