- Obesity may trigger anxiety-like behaviour through changes in brain function and gut bacteria
- A high-fat diet in mice led to increased anxiety symptoms and altered brain signalling
- Findings highlight the potential role of gut health in mental wellbeing and obesity-related conditions
New research from Georgia State University suggests that obesity may directly contribute to anxiety, with gut health playing a significant role in the relationship between physical and mental wellbeing.
The study, based on controlled experiments in mice, found that those fed a high-fat diet showed both increased body fat and more anxiety-like behaviours compared to those on a low-fat diet. These changes were linked to alterations in brain activity and gut microbiota – the community of bacteria living in the digestive system.
Gut-brain connection
Dr Desiree Wanders, associate professor and chair of nutrition at Georgia State University, explained that while previous studies have shown links between obesity and anxiety, this study suggests the connection may be more direct.
“Our findings suggest that obesity can lead to anxiety-like behaviour, possibly due to changes in both brain function and gut health,” she said.
The researchers used 32 male mice and monitored them from adolescence to early adulthood – a period comparable to the transition from teenage years to young adulthood in humans. Half of the mice were given a low-fat diet, while the others were fed a high-fat diet for 15 weeks.
At the end of the study, mice in the high-fat group had significantly greater body fat and weight. They also froze more frequently in behavioural tests, a sign of anxiety in animals.
Brain and microbiome changes
The team found that the hypothalamus – a brain region responsible for regulating metabolism – showed altered gene activity in obese mice, which could contribute to cognitive decline.
More notably, the gut microbiomes of obese mice were markedly different from those in the low-fat diet group. This supports the growing body of evidence that gut bacteria influence not only digestion, but also mood and mental function.
Dr Wanders emphasised the importance of viewing the body’s systems together.
“This research shows the strong links between diet, brain health and the gut microbiome. It suggests obesity could impact mental health in ways we’re only beginning to understand.”
Wider implications for public health
While the study was conducted in mice, the findings could have significant implications for humans – particularly younger individuals, who are increasingly affected by both obesity and anxiety.
Dr Wanders noted that while diet is important, it is only one part of the picture.
“Environmental influences, lifestyle, genetics and socio-economic status all play a role in obesity and mental health. Our study helps to explain one possible mechanism – but it’s clear this is a complex issue.”
The research team hopes to explore further how gut bacteria affect brain health and whether reversing obesity through dietary changes or weight loss can also reverse cognitive or emotional changes. They also aim to expand their studies to include female mice and different age groups.
These findings will be presented at NUTRITION 2025, the annual meeting of the American Society for Nutrition.