Junk food can be hard to resist. Those hamburgers, pizzas, fries, donuts, potato chips, sodas, and more are an affordable, easy snack or meal that fills you up when you’re on the go. Though the average American is steadily reducing their consumption of these unhealthy foods, fast food still makes up more than one-tenth of our total daily calories and in large part, is responsible for 60% of Americans being overweight or obese.

Of course, an occasional indulgence won’t hurt, but regularly eating these convenience foods will do more than cause you to pack on the pounds. Loaded with large amounts of saturated fats, salt, and sugar, and often lacking any significant nutritional value, junk foods have repeatedly been associated with a variety of health conditions including obesity, heart disease, diabetes, liver disease, fatigue, arthritis, and more.

Now, new research suggests it can destroy your memory.

Scientists have long been intrigued by the relationship between high-energy diets and impaired cognition. So, a team of researchers from the University of New South Wales decided to test the effects of unhealthy eating habits on the brain using animal models.

In the study published in the journal Brain, Behavior, and Immunity, investigators placed a group of lab rats on three separate diets. A control group ate a healthy diet of standard rat food, while a treatment group got the same diet, but supplemented with junk foods like cakes, chips, and biscuits. To isolate the effects of excess sugar intake, investigators assigned a third experimental group to eating a healthy diet, but with a 10 percent solution of sucrose.

Then, they compared cognition between all three groups.

The team discovered that test subjects consuming a diet rich in fat and sugar were simply unable to detect when an object was displaced to another location. Incredibly, those rats developed this impaired memory after just six days!

“What is so surprising about this research is the speed with which the deterioration of the cognition occurred,” said study lead author Professor Margaret Morris.

Her team found that the experimental rats fed a healthy diet along with sugar water suffered a fate similar to the treatment group. Additionally, both groups showed signs of inflammation in their hippocampus, that area of the brain associated with memory formation and storage, as well as spatial navigation. Interestingly, rats with the highest inflammation had the most severe memory loss, suggesting obesity causes changes in the brain and not just the body.

Researchers also discovered that the memory loss in both groups consuming a ‘junk food’ diet was irreversible!

“Our preliminary data also suggests that the damage is not reversed when the rats are switched back to a healthy diet, which is very concerning,” said Morris.

Due to a physiological likeness between rats and humans, Morris warned that her team’s findings are relevant to people of all ages, and highlights the importance of limiting the amount of junk food in our diets if we expect to live a long life free of disease.