WE ALL KNOW that chowing down on greasy fare from fast food joints isn’t good for your waistline or for your general health.

Consistently eating fried foods, which make up most of the options at these quickie stops, is known to promote inflammation in the body—and more inflammation can increase the risk of heart disease and diabetes.

The worst part? Eating junk food all the time stresses out your immune system. And because fast food hammers a genetic sensor called an inflammasome, eating a super-size burger all the time can keep your immune system on high alert for longer, leading to increased risk of developing diseases, says a new study published in the journal Cell.

In the study, researchers put mice on a typical “Western diet” similar to most fast food fare—high fat, high sugar, low fiber—for a month. After a month, the researchers discovered that the mice developed a significant inflammatory response—almost as if they’d come down with a bad bacteria infection. When they switched back to regular rodent chow, the inflammation calmed down, but the immune system remained primed to react strongly.

“The inflammasome triggers such epigenetic changes,” said study co-author Eicke Latz, Ph.D., director of the Institute for Innate Immunity at the University of Bonn in Germany. “The immune system consequently reacts even to small stimuli with stronger inflammatory responses. These findings…have important societal relevance. The foundations of a healthy diet need to become a much more prominent part of education than they are at present.”