Junk Food Promotes Anxiety

Obesity and anxiety disorders often occur together and are becoming more common in modern society, and inflammation is believed to play a key role in this connection⁽¹⁾.

Research in animal models shows that high-fat diet-induced obesity enhances neuroinflammation and anxiety-related defensive behavioral responses⁽²⁾.

Although the mechanism involved in the effects of high-fat diet on neuroinflammation and anxiety-related defensive behavioral responses are not fully elucidated, altered microbiome-gut-brain axis signaling is believed to play an imperative role. 

High-fat diet-induced changes in the diversity and community composition of the gut microbiome are central in determining health and disease through changes in innate immunity, inflammation, and cognitive function⁽³⁾.  

Gut dysbiosis – a condition where the microbiome exhibits an unhealthy imbalance in bacterial diversity and community composition – induces inflammation and neuroinflammation, alters brain serotonergic signaling, and increases anxiety-like defensive behavioral responses. 

The brain’s serotonergic system plays an important role in regulating emotional behavior, including anxiety-like defensive behavioral responses⁽⁴⁾.

Previous evidence indicates that animals fed a high-fat diet have a higher risk of developing anxiety-related defensive behaviors, but the underlying mechanisms remain unknown. Given the current knowledge gap, a recent study investigated if a high-fat diet alters the gut microbiome diversity and community composition, increases the serotonergic gene expression, and induces anxiety-related defensive behavioral responses⁽⁵⁾.
 
Adolescent rats were divided into two groups:

• Half got a standard diet of about 11% fat for nine weeks
• The others got a high-fat diet of 45% fat, consisting mostly of saturated fat from animal products. (According to the Centers for Disease Control and Prevention the typical American diet is about 36% fat)

Over the course of the research study, fecal samples were collected to assess the animals’ microbiome, or gut bacteria. After nine weeks, the animals underwent behavioral tests.

Main Findings

The study found that in animals, a high-fat diet disturbs resident gut bacteria, alters behavior and, through a complex pathway connecting the gut to the brain, influences brain chemicals in ways that feeds anxiety.

When compared to the control group, the group eating a high-fat diet, not surprisingly, gained weight. But the animals also showed significantly less gut bacteria diversity. Generally speaking, more bacterial diversity is associated with better health⁽⁶⁾.

The high-fat diet group also showed higher expression of three genes (tph2, htr1a, and slc6a4) involved in production and signaling of the neurotransmitter serotonin—particularly in a region of the brainstem known as the dorsal raphe nucleus, which is associated with stress and anxiety.

While serotonin is often hyped as a “feel-good brain chemical,” certain subsets of serotonin neurons can, when activated, prompt anxiety-like responses in animals. 

Notably, heightened expression of tph2, or tryptophan hydroxylase, in the dorsal raphe nucleus has been associated with mood disorders and suicide risk in humans. The high-fat group essentially had the molecular signature of a high anxiety state in their brain.
 
Researchers speculate that an unhealthy microbiome compromises the gut lining, permitting bacteria to slip into the body’s circulation and communicate with the brain via the vagus nerve, a pathway from the gastrointestinal tract to the brain.

Not all fats are bad, and healthy fats like those found in fish, olive oil, nuts and seeds can be anti-inflammatory and good for the brain⁽⁷⁾.

It is important to eat as many kinds of fruits and vegetables as possible, add fermented foods to your diet to support a healthy microbiome and lay off the pizza and fries

Summary

A high-fat diet can disrupt gut bacteria, alter behavior, and influence brain chemicals in ways that enhance anxiety. This research indicates that rats fed a high-fat diet showed less diversity in gut bacteria and higher expression of genes associated with stress and anxiety, suggesting that unhealthy eating habits may not only lead to weight gain but also negatively impact mental health.

Considering the early introduction of high-fat foods in children’s diets, and the ever-increasing obesity epidemic, this research presents a probable scenario by which the dietary choices during adolescence can influence the gut microbiome, brainstem serotonergic systems, and the susceptibility to the development of psychiatric disorders in adulthood.

This knowledge could lead to new microbiome-based approaches to prevent stress-related psychiatric disorders such as anxiety disorders.

When the digestive system is healthy with a good balance of bacteria, it can be expected to effectively filter out things that can damage your physical and mental health. Things such as bad bacteria and toxins are either stopped or mitigated from causing you harm.

The key to a healthy digestive system is eating a healthy diet made from real food made from whole food ingredients. That provides the foundation of a healthy gut microbiome. You can further fortify your gut and immune health by introducing more gut diversity and there may be no more efficient way than with a daily probiotic.

If you’re looking for a quick and effective way to improve your gut health consider adding Pro+Flora to your daily routine. 

Pro+Flora Probiotic helps you stay on point by providing your gut flora the fuel they need to keep you healthy and strong!

References:
    1.    Castanon N, Lasselin J, Capuron L: Neuropsychiatric comorbidity in obesity: role of inflammatory processes. Front Endocrinol (Lausanne) 5:74, 2014
    2.    Haleem DJ, Mahmood K: Brain serotonin in high-fat diet-induced weight gain, anxiety and spatial memory in rats. Nutr Neurosci 24:226-235, 2021
    3.    Yang Y, Du L, Shi D, et al: Dysbiosis of human gut microbiome in young-onset colorectal cancer. Nat Commun 12:6757, 2021
    4.    Donner NC, Kubala KH, Hassell JE, Jr., et al: Two models of inescapable stress increase tph2 mRNA expression in the anxiety-related dorsomedial part of the dorsal raphe nucleus. Neurobiol Stress 8:68-81, 2018
    5.    de Noronha SISR, de Moraes LAG, Hassell JE, et al: High-fat diet, microbiome-gut-brain axis signaling, and anxiety-like behavior in male rats. Biological Research 57:23, 2024
    6.    Manor O, Dai CL, Kornilov SA, et al: Health and disease markers correlate with gut microbiome composition across thousands of people. Nature Communications 11:5206, 2020
    7.    Chianese R, Coccurello R, Viggiano A, et al: Impact of Dietary Fats on Brain Functions. Curr Neuropharmacol 16:1059-1085, 2018