People often turn to highly processed and fatty foods to calm stress, but scientists at the University of Colorado, Boulder have discovered that some fatty foods can make anxiety worse.

According to Metro News, the researchers found that feeding animals a high-fat diet disrupted their gut bacteria, which triggered brain chemicals that fuel anxiety.

“Everyone knows that these items are not healthy foods, but we tend to think about them strictly in terms of a little weight gain. If you understand they also impact your brain in a way that can promote anxiety, that makes the stakes even higher,” said lead author Christopher Lowry, associate professor in the department of integrative physiology.

The study, published in the journal Biological Research, explained how male rats fed a high-fat diet not only gained weight during the nine-week course of research but also had less diverse gut microbiome. In addition, three genes associated with production of serotonin were more active in the high-fat group.

While most of us consider serotonin to be a “feel-good” hormone, the researchers said that certain nerve cells in the brain may generate an anxiety-like response when activated by this hormone. One of the three genes is called tryptophan hydroxylase, or tph 2, and is linked to mood disorders and suicide in humans.

Lowry suspects that high-fat diets make changes in the gut microbiome that allow unhealthy bacteria to travel through the vagus nerve to the brain causing reactions that promote anxiety. He adds that good fats, such as those found in avocados may help counteract the damage caused by “bad” fats such as those found in processed foods. Fats from plant sources, nuts and seeds may also have a protective, anti-inflammatory effect on the brain.