- High-fat diets, such as the typical Western diet, have been found to be associated with obesity and mental health disorders such as anxiety.
- A new study in mice suggests that obesity caused by a high-fat diet may alter the gut microbiome and gut-brain signaling, leading to changes that promote anxiety.
- Experts recommend supporting the gut microbiome and signaling pathways through a healthy diet and reducing intake of high-fat and highly processed foods.
Individuals with obesity are more likely to experience anxiety and other mental health disorders.
Among various overlapping factors, high-fat diets have been identified as a potential contributor to both obesity and anxiety. These diets can also alter the composition of our gut microbiome.
The gut microbiome may be an important link, as it can influence
These connections may help explain, in part, why obesity and anxiety often occur together.
To delve deeper into the complex relationships between high-fat diets, obesity, anxiety, and the gut microbiome, a new study examined the effects of a 9-week high-fat diet on mice.
The study analysed changes in the gut microbiome, the microbiome-gut-brain axis, and serotonin (serotonergic) systems in the brain. These systems are known to influence both anxiety and metabolism.
The results suggest that obesity induced by a high-fat diet may be associated with altered signaling on the microbiome-gut-serotonergic brain axis, resulting in increased anxiety-like behaviors in mice.
In other words, obesity caused by a high-fat diet can disrupt gut bacteria and their signaling pathways to the brain. This can ultimately affect brain chemicals associated with anxiety.
The findings have been published in
Researchers at the University of Colorado Boulder explored how high-fat diets affect the composition and diversity of the gut microbiome, the brain's serotonin systems, and anxiety-like behaviors.
For 9 weeks they studied two groups of mice:
- 12 rats were fed a control diet in which 11% of their daily calories came from fat
- 12 rats were fed a high-fat diet in which 45% of their daily calories came from fat
Stool samples were collected weekly to analyze gut microbiome changes, and behavioral tests were performed at the end of the study.
The researchers also measured diet-related changes in body composition, including final body weight, weight gain and fatness (body fat).
The results showed that the mice fed a high-fat diet gained more weight and body fat. They also had a significant decrease in gut microbiome diversity, which is generally associated with poor health.
These mice also had high levels of
Additionally, the high-fat diet group displayed increased expression of genes related to serotonin production and signaling within the dorsal raphe nucleus of the brain stem. This area of the brain is associated with stress and anxiety.
Although serotonin is often thought of as a “happy chemical,” some serotonin neurons can trigger behavioral responses such as temporary fear or anxiety when activated, the study authors explained.
The findings suggest that high-fat diets alter gut microbiome composition in a manner that is linked to increases in body fat and weight and changes in brain serotonin systems related to anxiety.
Medical News Today We spoke to Thomas M. Holland, M.D., M.S., a physician-scientist and assistant professor at the RUSH Institute for Healthy Aging, RUSH University, College of Health Sciences, who was not involved in the study.
They added that a high-fat diet “decreases the overall diversity of the gut microbiome, leading to a less complex microbial community [which] can impair the gut’s ability to maintain a balanced environment.”
MNT They also spoke with nutritional neuroscientist and doctor of health sciences candidate Timothy Fry, MS, who holds a certification in nutritional psychology from the Center for Nutritional Psychology, who was not involved in the study.
He further added, “[t]“The microbiome-gut-serotonergic brain axis represents an important communication pathway between the gut microbiota and the brain, particularly focusing on serotonin, a neurotransmitter essential for mood regulation.”
“Serotonin is primarily produced in the gut,
about 95% of the body's serotonin Found in the gastrointestinal tract. The gut microbiota influences the production and function of serotonin through the synthesis of its precursor, tryptophan, and the modulation of serotonergic receptors and transporters.
— Timothy Frye, MS
“The importance of this axis in mental health is profound. Changes in the gut microbiome can lead to disturbances in serotonin levels, which may impact mood, anxiety and overall mental health,” Frey said.
For example, he said, an imbalance in the microbial community (gut dysbiosis) can result in increased gut permeability, systemic inflammation, and alterations in serotonin signaling.
According to Frye, this can cause or worsen mental health conditions such as anxiety, post-traumatic stress disorder and depression.
“Understanding this axis opens new avenues for therapeutic interventions targeting the gut microbiome to regulate brain function and improve mental health outcomes,” he added.
“A diet rich in saturated fat and low in fiber may reduce bacterial diversity and alter the balance of gut bacteria, as seen in mice,” Holland said.
In addition, he said, “[h]Human studies have shown that diets high in saturated fat and low in healthy nutrients are associated with higher rates of anxiety and depression.”
“The behavioral changes observed in mice provide a possible mechanistic explanation for these relationships in humans,” Holland explained.
Frye further stated that “[w]Although there are inherent differences between mice and humans, many physiological and biochemical pathways are conserved across the different species.”
“The basic principles of the microbiome-gut-brain axis, elucidated in studies on mice, provide valuable information applicable to human health. In both mice and humans, diet-induced changes in the gut microbiome may significantly influence brain function and behavior through similar mechanisms.”
— Timothy Frye, MS
He added, “Human studies have confirmed findings from rodent models, showing that dietary interventions can modify the gut microbiome, influence serotonin levels, and affect mental health.”
Although the study findings provide information about potential therapeutic interventions for mental health, the mechanisms underlying the observed changes were not directly investigated.
The current study also has other notable limitations, such as that it only included male mice of certain ages, raising questions about the applicability of the findings to females or other life stages.
The study authors suggest that future research should take these factors into account, especially given the higher incidence of anxiety and other mental health disorders in women.
Overall, more research is needed to fully understand the microbiome-gut-serotonergic brain axis and its impact on human health.
,[This study’s] “Our findings underscore the importance of dietary interventions in the treatment of anxiety disorders, particularly for individuals with obesity,” Holland said.
He emphasized that, “By improving dietary habits, such as increasing intake of healthy fats and decreasing unhealthy fats, individuals can support better gut-brain signaling, reduce inflammation, and enhance overall mental health.”
Holland specifically recommends increasing your intake of the following:
- Foods rich in omega-3, Fatty fish, flax seeds, chia seeds, hemp seeds, and walnuts
- Fermented foods, Yogurt with live cultures, kefir, sauerkraut, kimchi, miso, and tempeh
- Prebiotic foods, Garlic, onions, leeks, asparagus, bananas and oats
- Dark Leafy Greens, Spinach, kale, Swiss chard, arugula, and collard greens
- Jamun: Blueberries, strawberries, raspberries and blackberries
Similarly, Frey recommends eating a diet rich in omega-3s, fermented foods, and fiber from fruits, vegetables, and whole grains to promote the growth of beneficial gut bacteria, enhancing microbial diversity and gut health.
Additionally, both experts highlighted the importance of hydration for overall and digestive health and recommended meeting daily water requirements.
“Ensuring adequate fiber intake, including probiotic and prebiotic foods, and maintaining proper hydration will promote a healthy gut microbiome, reduce inflammation, support overall brain health, and improve mood and anxiety levels,” Holland said.
Holland also suggested reducing your intake of foods high in trans and saturated fats, fast and fried foods, dark red meat and high-fat dairy products.
“Limiting your intake of high-fat and processed foods helps prevent gut dysbiosis and reduce inflammation, leading to better gut-brain communication,” Frye agreed.