High-Fat Diet Linked to Increased Anxiety

A new study from the University of Colorado Boulder suggests that turning to junk food when stressed can exacerbate anxiety rather than providing comfort. The research, led by Professor Christopher Lowry, found that a high-fat diet disrupts gut bacteria, alters behavior, and influences brain chemicals through the gut-brain axis, fueling anxiety.

Lowry’s team conducted the study using adolescent rats, dividing them into two groups. One group received a standard diet with about 11% fat, while the other was given a high-fat diet consisting of 45% fat, primarily from animal products. This high-fat diet mirrors the typical American diet, which is about 36% fat according to the Centers for Disease Control and Prevention (CDC).

The researchers collected fecal samples from the rats to analyze their gut microbiome throughout the study. After nine weeks, behavioral tests were performed on the animals. The high-fat diet group gained weight and exhibited significantly less diversity in their gut bacteria. Generally, higher bacterial diversity is linked to better health. This group also had a higher ratio of Firmicutes to Bacteroidetes, a bacterial ratio associated with industrialized diets and obesity.

Moreover, the high-fat diet group showed increased expression of three genes (tph2, htr1a, and slc6a4) involved in the production and signaling of serotonin, particularly in the dorsal raphe nucleus (cDRD) region of the brainstem, which is associated with stress and anxiety. Although serotonin is often known as a “feel-good brain chemical,” certain subsets of serotonin neurons can induce anxiety-like responses when activated. Notably, increased expression of the tph2 gene in the cDRD has been linked to mood disorders and suicide risk in humans.

“The high-fat group essentially had the molecular signature of a high anxiety state in their brain,” said Lowry. He explained that an unhealthy microbiome might compromise the gut lining, allowing bacteria to enter the bloodstream and communicate with the brain via the vagus nerve. This pathway from the gastrointestinal tract to the brain may explain why certain diets impact mental health.

Lowry pointed out that not all fats are harmful. Healthy fats found in fish, olive oil, nuts, and seeds can be anti-inflammatory and beneficial for the brain. He advised consuming a variety of fruits and vegetables, incorporating fermented foods to support a healthy microbiome, and avoiding high-fat junk food like pizza and fries. Additionally, adding healthy fats such as avocado to meals could mitigate some of the negative effects of unhealthy fats. This study highlights the importance of diet on mental health, particularly in how high-fat diets can negatively impact the gut-brain axis, leading to increased anxiety. By understanding the role of gut bacteria and serotonin signaling, we can better comprehend how diet influences behavior and mental health, paving the way for more effective dietary recommendations and treatments for stress and anxiety.

Story Source: University of Colorado at Boulder [Link]. Original written by Lisa Marshall. Content may be edited for style and length.