Do high-fat diets worsen anxiety? Scientists find link in study on mice

Fatty foods are notorious for their weight-gaining properties, but a new study has discovered that a high-fat diet may come with yet another unwanted side effect — anxiety.

The University of Colorado Boulder recently researched the fatty foods many people turn to when stressed. The animal study, published in the journal Biological Research last month, discovered that a high-fat diet disrupted gut bacteria, altered behavior and influenced brain chemicals related to anxiety.

“Everyone knows that these are not healthy foods, but we tend to think about them strictly in terms of a little weight gain,” University of Colorado Boulder integrative physiology professor and lead study author Christopher Lowry said in a news release.

“If you understand that they also impact your brain in a way that can promote anxiety, that makes the stakes even higher,” he added.

Lowry and his team divided rats into two groups for the study. One group was given a standard 11% fat diet, while the other was given a 45% fat diet consisting mostly of saturated fats from animal products. By comparison, U.S. adults averaged 35.8% fat in their diets in 2018.

The rats fed a high-fat diet showed higher expressions of three genes involved in the production of serotonin, a neurotransmitter linked to stress and anxiety. The “feel-good brain chemical” can prompt anxiety responses in animals. In humans, the same neurotransmitter subset is associated with mood disorders and heightened suicide risk.

“To think that just a high-fat diet could alter expression of these genes in the brain is extraordinary,” Lowry said. “The high-fat group essentially had the molecular signature of a high anxiety state in their brain.”

The researcher pointed out, however, that not all fats are bad. The fats found in fish, olive oil, nuts and seeds are healthy, but his study discovered that a diet high in saturated fats may increase anxiety and susceptibility to future stress.

To better understand how high-fat diets affect humans differently that rats will still take further research, the researchers conceded.