How a high-fat diet can promote anxiety

Dietary choices have a significant impact on our mental health. A recent study demonstrates that a diet rich in saturated fats could increase anxiety.


Published in Biological Research, this research conducted by scientists from the universities of Boulder in Colorado and Ouro Preto in Brazil shows that fatty foods disrupt the gut microbiota and alter certain chemicals in the brain, thereby triggering anxious behaviors.

High-fat diet: reduced microbial diversity

The team previously observed an increase in neuroinflammation and anxious behaviors in rats fed a diet high in saturated fats. In this new study, they aimed to understand the link between fat consumption and anxiety. Two groups of rats were studied: the first group received a standard diet containing about 11% fats, while the second group was fed a diet containing 45% fats, mainly saturated. This experiment lasted nine weeks.

Throughout the study, fecal samples were collected to analyze the animals' gut microbiota. Behavioral tests showed that the rats in the high-fat group gained weight and exhibited lower bacterial diversity in their intestines. Christopher Lowry, the lead author of the study, points out that greater bacterial diversity generally correlates with better health.

Additionally, the rats in the high-fat group showed increased expression of three genes (tph2, htr1a, slc6a4) involved in the production and signaling of serotonin, a neurotransmitter often associated with happiness. However, certain serotonin neurons can also trigger anxious reactions. In humans, high tph2 expression has been linked to mood disorders and an increased risk of suicide.

Mechanisms linking gut microbiota and the brain

Christopher Lowry explains that the disruption of the gut microbiota could compromise the intestinal lining, allowing bacteria to enter the bloodstream and interact with the brain via the vagus nerve. This gut-brain connection could be behind the chemical changes observed in the brain.

However, Lowry reminds us that not all fats are harmful. Healthy fats, such as those found in fish, olive oil, nuts, and seeds, are anti-inflammatory and beneficial for the brain. On the other hand, excessive consumption of saturated fats can increase the risk of anxiety. He advises adopting a diverse diet and including fermented foods to support a healthy microbiota. Avoiding foods rich in saturated fats, like pizzas and fries, can help reduce the risk of anxiety.