Changes to gut microbiome due to high-fat diets key to obesity, anxiety: Study

Hyderabad: Recent studies have identified a strong link between high-fat diets, obesity, anxiety, and changes in the gut microbiome. The article talks about how the intricate relationships among these factors could help explain why obesity and anxiety often occur together.

Studying high-fat diets, obesity, and anxiety in rats

Researchers from the University of Colorado Boulder investigated the effects of high-fat diets on rats over nine weeks. The study analysed shifts in the gut microbiome, the microbiome-gut-brain axis, and the serotonergic systems in the brain, which influence both anxiety and metabolism.

The study divided rats into two groups: one fed a control diet with 11 per cent of daily calories from fat and the other fed a high-fat diet with 45 per cent of daily calories from fat. Weekly faecal samples were collected to analyse gut microbiome changes, and behavioural tests were conducted at the end of the study.

Key findings

1. Weight and Body Fat: Rats on the high-fat diet gained more weight and body fat compared to the control group.

2. Gut Microbiome: The high-fat diet group had significantly lower gut microbiome diversity, which is generally linked to poorer health. They also had a higher Firmicutes to Bacteroidetes bacteria ratio, a marker of dysbiosis often associated with obesity.

3. Brain Serotonin Systems: The high-fat diet group showed increased expression of genes related to serotonin production and signalling within the brainstem’s dorsal raphe nucleus, an area linked to stress and anxiety.

Expert insights

Dr Anitha Reddy, a gastroenterologist from Hyderabad, emphasised the importance of avoiding high-fat and processed foods to maintain gut health.

Dr Vinay Kumar, a psychiatrist from Hyderabad, suggested that dietary changes should be part of the treatment plan for patients with anxiety.

Thomas M Holland, MD, MS, a physician-scientist at the RUSH Institute for Healthy Aging, explained that a high-fat diet ‘tends to reduce 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.’

Timothy Frie, MS, a nutritional neuroscientist, added, “The microbiome-gut-serotonergic brain axis represents a critical communication pathway between the gut microbiota and the brain, particularly focusing on serotonin, a neurotransmitter essential for mood regulation.”

Relevance to human health

Dr Kumar noted, “Human studies have shown that diets high in saturated fats and low in healthy nutrients are associated with higher rates of anxiety and depression. The behavioural changes observed in rats provide a potential mechanistic explanation for these associations in humans.”

He pointed out that while there are differences between rats and humans, many physiological and biochemical pathways are conserved across species.

“Human studies have corroborated findings from rodent models, showing that dietary interventions can modulate the gut microbiome, affect serotonin levels and impact mental health,” he said.

Recommendations for improving gut health

- Omega-3-rich foods: fatty fish, flaxseeds, 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.

- Berries: blueberries, strawberries, raspberries and blackberries.

The study also highlighted the importance of hydration and reducing the intake of high-trans and saturated-fat foods, fast and fried foods, dark red meat, and high-fat dairy products.

“Understanding the link between high-fat diets, gut health and anxiety opens new avenues for potential therapeutic interventions. Improving dietary habits can support better gut-brain signalling, reduce inflammation, and enhance overall mental health. This research underscores the importance of dietary choices in managing obesity and anxiety, offering insights into improving mental health through gut health interventions,” noted Dr Reddy.