(NewsNation) — New research from the University of Colorado Boulder suggests high-fat diets may disrupt gut bacteria and fuel anxiety.

Researchers divided male adolescent rats into two groups and fed half a standard diet of about 11% fat for nine weeks. The other group at a diet of about 45% fat, comprised mostly of saturated fat from animal products, according to a news release.

An American diet typically consists of about 36% fat, according to the U.S. Centers for Disease Control and Prevention.

During the course of the study, researchers examined the rats’ gut bacteria through fecal samples. The animals also underwent behavioral tests after nine weeks.

Researchers found that the group eating the high-fat diet not only gained weight but also had significantly fewer diverse gut bacteria. Those rats also showed higher expression of genes involved in the production and signaling of serotonin, especially in a part of the brainstem associated with stress and anxiety.

Although serotonin is often associated with eating food, different subsets of serotonin can trigger “anxiety-like responses” in animals, said lead author Christopher Lowry, a professor of integrative physiology at CU Boulder.

According to Lowry, people should limit their intake of high-fat foods, eat a variety of fruits and vegetables and add fermented foods to their diet to support a healthy microbiome.